PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
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// SPDX-License-Identifier: GPL-2.0
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/*
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* PCI Peer 2 Peer DMA support.
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*
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* Copyright (c) 2016-2018, Logan Gunthorpe
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* Copyright (c) 2016-2017, Microsemi Corporation
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* Copyright (c) 2017, Christoph Hellwig
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* Copyright (c) 2018, Eideticom Inc.
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*/
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2018-10-04 15:27:38 -06:00
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#define pr_fmt(fmt) "pci-p2pdma: " fmt
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#include <linux/ctype.h>
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
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#include <linux/pci-p2pdma.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/genalloc.h>
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#include <linux/memremap.h>
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#include <linux/percpu-refcount.h>
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#include <linux/random.h>
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#include <linux/seq_buf.h>
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2019-06-19 12:56:26 -06:00
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#include <linux/iommu.h>
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PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
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struct pci_p2pdma {
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struct gen_pool *pool;
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bool p2pmem_published;
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};
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2018-10-04 15:27:36 -06:00
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static ssize_t size_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct pci_dev *pdev = to_pci_dev(dev);
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size_t size = 0;
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if (pdev->p2pdma->pool)
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size = gen_pool_size(pdev->p2pdma->pool);
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return snprintf(buf, PAGE_SIZE, "%zd\n", size);
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}
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static DEVICE_ATTR_RO(size);
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static ssize_t available_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct pci_dev *pdev = to_pci_dev(dev);
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size_t avail = 0;
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if (pdev->p2pdma->pool)
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avail = gen_pool_avail(pdev->p2pdma->pool);
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return snprintf(buf, PAGE_SIZE, "%zd\n", avail);
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}
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static DEVICE_ATTR_RO(available);
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static ssize_t published_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct pci_dev *pdev = to_pci_dev(dev);
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return snprintf(buf, PAGE_SIZE, "%d\n",
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pdev->p2pdma->p2pmem_published);
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}
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static DEVICE_ATTR_RO(published);
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static struct attribute *p2pmem_attrs[] = {
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&dev_attr_size.attr,
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&dev_attr_available.attr,
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&dev_attr_published.attr,
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NULL,
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};
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static const struct attribute_group p2pmem_group = {
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.attrs = p2pmem_attrs,
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.name = "p2pmem",
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};
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|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
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static void pci_p2pdma_release(void *data)
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{
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struct pci_dev *pdev = data;
|
2019-06-13 16:56:30 -06:00
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struct pci_p2pdma *p2pdma = pdev->p2pdma;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
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|
2019-06-13 16:56:30 -06:00
|
|
|
if (!p2pdma)
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
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|
return;
|
|
|
|
|
2019-06-13 16:56:30 -06:00
|
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/* Flush and disable pci_alloc_p2p_mem() */
|
|
|
|
pdev->p2pdma = NULL;
|
|
|
|
synchronize_rcu();
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
2019-06-13 16:56:30 -06:00
|
|
|
gen_pool_destroy(p2pdma->pool);
|
2018-10-04 15:27:36 -06:00
|
|
|
sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
static int pci_p2pdma_setup(struct pci_dev *pdev)
|
|
|
|
{
|
|
|
|
int error = -ENOMEM;
|
|
|
|
struct pci_p2pdma *p2p;
|
|
|
|
|
|
|
|
p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
|
|
|
|
if (!p2p)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
|
|
|
|
if (!p2p->pool)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
|
|
|
|
if (error)
|
|
|
|
goto out_pool_destroy;
|
|
|
|
|
|
|
|
pdev->p2pdma = p2p;
|
|
|
|
|
2018-10-04 15:27:36 -06:00
|
|
|
error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
|
|
|
|
if (error)
|
|
|
|
goto out_pool_destroy;
|
|
|
|
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
return 0;
|
|
|
|
|
|
|
|
out_pool_destroy:
|
2018-10-04 15:27:36 -06:00
|
|
|
pdev->p2pdma = NULL;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
gen_pool_destroy(p2p->pool);
|
|
|
|
out:
|
|
|
|
devm_kfree(&pdev->dev, p2p);
|
|
|
|
return error;
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_p2pdma_add_resource - add memory for use as p2p memory
|
|
|
|
* @pdev: the device to add the memory to
|
|
|
|
* @bar: PCI BAR to add
|
|
|
|
* @size: size of the memory to add, may be zero to use the whole BAR
|
|
|
|
* @offset: offset into the PCI BAR
|
|
|
|
*
|
|
|
|
* The memory will be given ZONE_DEVICE struct pages so that it may
|
|
|
|
* be used with any DMA request.
|
|
|
|
*/
|
|
|
|
int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
|
|
|
|
u64 offset)
|
|
|
|
{
|
|
|
|
struct dev_pagemap *pgmap;
|
|
|
|
void *addr;
|
|
|
|
int error;
|
|
|
|
|
|
|
|
if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
|
|
|
|
return -EINVAL;
|
|
|
|
|
|
|
|
if (offset >= pci_resource_len(pdev, bar))
|
|
|
|
return -EINVAL;
|
|
|
|
|
|
|
|
if (!size)
|
|
|
|
size = pci_resource_len(pdev, bar) - offset;
|
|
|
|
|
|
|
|
if (size + offset > pci_resource_len(pdev, bar))
|
|
|
|
return -EINVAL;
|
|
|
|
|
|
|
|
if (!pdev->p2pdma) {
|
|
|
|
error = pci_p2pdma_setup(pdev);
|
|
|
|
if (error)
|
|
|
|
return error;
|
|
|
|
}
|
|
|
|
|
2019-06-26 06:27:16 -06:00
|
|
|
pgmap = devm_kzalloc(&pdev->dev, sizeof(*pgmap), GFP_KERNEL);
|
|
|
|
if (!pgmap)
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
return -ENOMEM;
|
|
|
|
pgmap->res.start = pci_resource_start(pdev, bar) + offset;
|
|
|
|
pgmap->res.end = pgmap->res.start + size - 1;
|
|
|
|
pgmap->res.flags = pci_resource_flags(pdev, bar);
|
|
|
|
pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
|
2018-10-04 15:27:37 -06:00
|
|
|
pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) -
|
|
|
|
pci_resource_start(pdev, bar);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
|
|
|
addr = devm_memremap_pages(&pdev->dev, pgmap);
|
|
|
|
if (IS_ERR(addr)) {
|
|
|
|
error = PTR_ERR(addr);
|
2019-06-13 16:56:33 -06:00
|
|
|
goto pgmap_free;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
}
|
|
|
|
|
2019-06-13 16:56:30 -06:00
|
|
|
error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
pci_bus_address(pdev, bar) + offset,
|
2019-06-13 16:56:30 -06:00
|
|
|
resource_size(&pgmap->res), dev_to_node(&pdev->dev),
|
2019-06-26 06:27:16 -06:00
|
|
|
pgmap->ref);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
if (error)
|
2019-06-13 16:56:24 -06:00
|
|
|
goto pages_free;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
|
|
|
pci_info(pdev, "added peer-to-peer DMA memory %pR\n",
|
|
|
|
&pgmap->res);
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
|
2019-06-13 16:56:24 -06:00
|
|
|
pages_free:
|
|
|
|
devm_memunmap_pages(&pdev->dev, pgmap);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
pgmap_free:
|
2019-06-26 06:27:16 -06:00
|
|
|
devm_kfree(&pdev->dev, pgmap);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
return error;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Note this function returns the parent PCI device with a
|
2019-05-30 07:05:58 -06:00
|
|
|
* reference taken. It is the caller's responsibility to drop
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
* the reference.
|
|
|
|
*/
|
|
|
|
static struct pci_dev *find_parent_pci_dev(struct device *dev)
|
|
|
|
{
|
|
|
|
struct device *parent;
|
|
|
|
|
|
|
|
dev = get_device(dev);
|
|
|
|
|
|
|
|
while (dev) {
|
|
|
|
if (dev_is_pci(dev))
|
|
|
|
return to_pci_dev(dev);
|
|
|
|
|
|
|
|
parent = get_device(dev->parent);
|
|
|
|
put_device(dev);
|
|
|
|
dev = parent;
|
|
|
|
}
|
|
|
|
|
|
|
|
return NULL;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Check if a PCI bridge has its ACS redirection bits set to redirect P2P
|
|
|
|
* TLPs upstream via ACS. Returns 1 if the packets will be redirected
|
|
|
|
* upstream, 0 otherwise.
|
|
|
|
*/
|
|
|
|
static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
|
|
|
|
{
|
|
|
|
int pos;
|
|
|
|
u16 ctrl;
|
|
|
|
|
|
|
|
pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
|
|
|
|
if (!pos)
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
|
|
|
|
|
|
|
|
if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
|
|
|
|
{
|
|
|
|
if (!buf)
|
|
|
|
return;
|
|
|
|
|
|
|
|
seq_buf_printf(buf, "%s;", pci_name(pdev));
|
|
|
|
}
|
|
|
|
|
2019-04-18 05:58:59 -06:00
|
|
|
/*
|
|
|
|
* If we can't find a common upstream bridge take a look at the root
|
|
|
|
* complex and compare it to a whitelist of known good hardware.
|
|
|
|
*/
|
|
|
|
static bool root_complex_whitelist(struct pci_dev *dev)
|
|
|
|
{
|
|
|
|
struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
|
|
|
|
struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
|
|
|
|
unsigned short vendor, device;
|
|
|
|
|
2019-06-19 12:56:26 -06:00
|
|
|
if (iommu_present(dev->dev.bus))
|
|
|
|
return false;
|
|
|
|
|
2019-04-18 05:58:59 -06:00
|
|
|
if (!root)
|
|
|
|
return false;
|
|
|
|
|
|
|
|
vendor = root->vendor;
|
|
|
|
device = root->device;
|
|
|
|
pci_dev_put(root);
|
|
|
|
|
|
|
|
/* AMD ZEN host bridges can do peer to peer */
|
|
|
|
if (vendor == PCI_VENDOR_ID_AMD && device == 0x1450)
|
|
|
|
return true;
|
|
|
|
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
/*
|
|
|
|
* Find the distance through the nearest common upstream bridge between
|
|
|
|
* two PCI devices.
|
|
|
|
*
|
|
|
|
* If the two devices are the same device then 0 will be returned.
|
|
|
|
*
|
|
|
|
* If there are two virtual functions of the same device behind the same
|
|
|
|
* bridge port then 2 will be returned (one step down to the PCIe switch,
|
|
|
|
* then one step back to the same device).
|
|
|
|
*
|
|
|
|
* In the case where two devices are connected to the same PCIe switch, the
|
|
|
|
* value 4 will be returned. This corresponds to the following PCI tree:
|
|
|
|
*
|
|
|
|
* -+ Root Port
|
|
|
|
* \+ Switch Upstream Port
|
|
|
|
* +-+ Switch Downstream Port
|
|
|
|
* + \- Device A
|
|
|
|
* \-+ Switch Downstream Port
|
|
|
|
* \- Device B
|
|
|
|
*
|
|
|
|
* The distance is 4 because we traverse from Device A through the downstream
|
|
|
|
* port of the switch, to the common upstream port, back up to the second
|
|
|
|
* downstream port and then to Device B.
|
|
|
|
*
|
|
|
|
* Any two devices that don't have a common upstream bridge will return -1.
|
|
|
|
* In this way devices on separate PCIe root ports will be rejected, which
|
|
|
|
* is what we want for peer-to-peer seeing each PCIe root port defines a
|
|
|
|
* separate hierarchy domain and there's no way to determine whether the root
|
|
|
|
* complex supports forwarding between them.
|
|
|
|
*
|
|
|
|
* In the case where two devices are connected to different PCIe switches,
|
|
|
|
* this function will still return a positive distance as long as both
|
|
|
|
* switches eventually have a common upstream bridge. Note this covers
|
|
|
|
* the case of using multiple PCIe switches to achieve a desired level of
|
|
|
|
* fan-out from a root port. The exact distance will be a function of the
|
|
|
|
* number of switches between Device A and Device B.
|
|
|
|
*
|
|
|
|
* If a bridge which has any ACS redirection bits set is in the path
|
|
|
|
* then this functions will return -2. This is so we reject any
|
|
|
|
* cases where the TLPs are forwarded up into the root complex.
|
|
|
|
* In this case, a list of all infringing bridge addresses will be
|
|
|
|
* populated in acs_list (assuming it's non-null) for printk purposes.
|
|
|
|
*/
|
2019-04-18 05:58:59 -06:00
|
|
|
static int upstream_bridge_distance(struct pci_dev *provider,
|
|
|
|
struct pci_dev *client,
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
struct seq_buf *acs_list)
|
|
|
|
{
|
2019-04-18 05:58:59 -06:00
|
|
|
struct pci_dev *a = provider, *b = client, *bb;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
int dist_a = 0;
|
|
|
|
int dist_b = 0;
|
|
|
|
int acs_cnt = 0;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Note, we don't need to take references to devices returned by
|
|
|
|
* pci_upstream_bridge() seeing we hold a reference to a child
|
|
|
|
* device which will already hold a reference to the upstream bridge.
|
|
|
|
*/
|
|
|
|
|
|
|
|
while (a) {
|
|
|
|
dist_b = 0;
|
|
|
|
|
|
|
|
if (pci_bridge_has_acs_redir(a)) {
|
|
|
|
seq_buf_print_bus_devfn(acs_list, a);
|
|
|
|
acs_cnt++;
|
|
|
|
}
|
|
|
|
|
|
|
|
bb = b;
|
|
|
|
|
|
|
|
while (bb) {
|
|
|
|
if (a == bb)
|
|
|
|
goto check_b_path_acs;
|
|
|
|
|
|
|
|
bb = pci_upstream_bridge(bb);
|
|
|
|
dist_b++;
|
|
|
|
}
|
|
|
|
|
|
|
|
a = pci_upstream_bridge(a);
|
|
|
|
dist_a++;
|
|
|
|
}
|
|
|
|
|
2019-04-18 05:58:59 -06:00
|
|
|
/*
|
|
|
|
* Allow the connection if both devices are on a whitelisted root
|
2019-05-30 07:05:58 -06:00
|
|
|
* complex, but add an arbitrary large value to the distance.
|
2019-04-18 05:58:59 -06:00
|
|
|
*/
|
|
|
|
if (root_complex_whitelist(provider) &&
|
|
|
|
root_complex_whitelist(client))
|
|
|
|
return 0x1000 + dist_a + dist_b;
|
|
|
|
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
return -1;
|
|
|
|
|
|
|
|
check_b_path_acs:
|
|
|
|
bb = b;
|
|
|
|
|
|
|
|
while (bb) {
|
|
|
|
if (a == bb)
|
|
|
|
break;
|
|
|
|
|
|
|
|
if (pci_bridge_has_acs_redir(bb)) {
|
|
|
|
seq_buf_print_bus_devfn(acs_list, bb);
|
|
|
|
acs_cnt++;
|
|
|
|
}
|
|
|
|
|
|
|
|
bb = pci_upstream_bridge(bb);
|
|
|
|
}
|
|
|
|
|
|
|
|
if (acs_cnt)
|
|
|
|
return -2;
|
|
|
|
|
|
|
|
return dist_a + dist_b;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int upstream_bridge_distance_warn(struct pci_dev *provider,
|
|
|
|
struct pci_dev *client)
|
|
|
|
{
|
|
|
|
struct seq_buf acs_list;
|
|
|
|
int ret;
|
|
|
|
|
|
|
|
seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
|
|
|
|
if (!acs_list.buffer)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
ret = upstream_bridge_distance(provider, client, &acs_list);
|
|
|
|
if (ret == -2) {
|
|
|
|
pci_warn(client, "cannot be used for peer-to-peer DMA as ACS redirect is set between the client and provider (%s)\n",
|
|
|
|
pci_name(provider));
|
|
|
|
/* Drop final semicolon */
|
|
|
|
acs_list.buffer[acs_list.len-1] = 0;
|
|
|
|
pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
|
|
|
|
acs_list.buffer);
|
|
|
|
|
|
|
|
} else if (ret < 0) {
|
|
|
|
pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge\n",
|
|
|
|
pci_name(provider));
|
|
|
|
}
|
|
|
|
|
|
|
|
kfree(acs_list.buffer);
|
|
|
|
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
2019-05-30 07:05:58 -06:00
|
|
|
* pci_p2pdma_distance_many - Determine the cumulative distance between
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
* a p2pdma provider and the clients in use.
|
|
|
|
* @provider: p2pdma provider to check against the client list
|
|
|
|
* @clients: array of devices to check (NULL-terminated)
|
|
|
|
* @num_clients: number of clients in the array
|
|
|
|
* @verbose: if true, print warnings for devices when we return -1
|
|
|
|
*
|
|
|
|
* Returns -1 if any of the clients are not compatible (behind the same
|
|
|
|
* root port as the provider), otherwise returns a positive number where
|
2018-12-01 10:31:34 -07:00
|
|
|
* a lower number is the preferable choice. (If there's one client
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
* that's the same as the provider it will return 0, which is best choice).
|
|
|
|
*
|
|
|
|
* For now, "compatible" means the provider and the clients are all behind
|
|
|
|
* the same PCI root port. This cuts out cases that may work but is safest
|
|
|
|
* for the user. Future work can expand this to white-list root complexes that
|
|
|
|
* can safely forward between each ports.
|
|
|
|
*/
|
|
|
|
int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
|
|
|
|
int num_clients, bool verbose)
|
|
|
|
{
|
|
|
|
bool not_supported = false;
|
|
|
|
struct pci_dev *pci_client;
|
|
|
|
int distance = 0;
|
|
|
|
int i, ret;
|
|
|
|
|
|
|
|
if (num_clients == 0)
|
|
|
|
return -1;
|
|
|
|
|
|
|
|
for (i = 0; i < num_clients; i++) {
|
2019-07-02 11:35:44 -06:00
|
|
|
if (IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
|
|
|
|
clients[i]->dma_ops == &dma_virt_ops) {
|
|
|
|
if (verbose)
|
|
|
|
dev_warn(clients[i],
|
|
|
|
"cannot be used for peer-to-peer DMA because the driver makes use of dma_virt_ops\n");
|
|
|
|
return -1;
|
|
|
|
}
|
|
|
|
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
pci_client = find_parent_pci_dev(clients[i]);
|
|
|
|
if (!pci_client) {
|
|
|
|
if (verbose)
|
|
|
|
dev_warn(clients[i],
|
|
|
|
"cannot be used for peer-to-peer DMA as it is not a PCI device\n");
|
|
|
|
return -1;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (verbose)
|
|
|
|
ret = upstream_bridge_distance_warn(provider,
|
|
|
|
pci_client);
|
|
|
|
else
|
|
|
|
ret = upstream_bridge_distance(provider, pci_client,
|
|
|
|
NULL);
|
|
|
|
|
|
|
|
pci_dev_put(pci_client);
|
|
|
|
|
|
|
|
if (ret < 0)
|
|
|
|
not_supported = true;
|
|
|
|
|
|
|
|
if (not_supported && !verbose)
|
|
|
|
break;
|
|
|
|
|
|
|
|
distance += ret;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (not_supported)
|
|
|
|
return -1;
|
|
|
|
|
|
|
|
return distance;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_has_p2pmem - check if a given PCI device has published any p2pmem
|
|
|
|
* @pdev: PCI device to check
|
|
|
|
*/
|
|
|
|
bool pci_has_p2pmem(struct pci_dev *pdev)
|
|
|
|
{
|
|
|
|
return pdev->p2pdma && pdev->p2pdma->p2pmem_published;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_has_p2pmem);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_p2pmem_find - find a peer-to-peer DMA memory device compatible with
|
|
|
|
* the specified list of clients and shortest distance (as determined
|
|
|
|
* by pci_p2pmem_dma())
|
|
|
|
* @clients: array of devices to check (NULL-terminated)
|
|
|
|
* @num_clients: number of client devices in the list
|
|
|
|
*
|
|
|
|
* If multiple devices are behind the same switch, the one "closest" to the
|
2018-12-01 10:31:34 -07:00
|
|
|
* client devices in use will be chosen first. (So if one of the providers is
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
* the same as one of the clients, that provider will be used ahead of any
|
|
|
|
* other providers that are unrelated). If multiple providers are an equal
|
|
|
|
* distance away, one will be chosen at random.
|
|
|
|
*
|
|
|
|
* Returns a pointer to the PCI device with a reference taken (use pci_dev_put
|
|
|
|
* to return the reference) or NULL if no compatible device is found. The
|
|
|
|
* found provider will also be assigned to the client list.
|
|
|
|
*/
|
|
|
|
struct pci_dev *pci_p2pmem_find_many(struct device **clients, int num_clients)
|
|
|
|
{
|
|
|
|
struct pci_dev *pdev = NULL;
|
|
|
|
int distance;
|
|
|
|
int closest_distance = INT_MAX;
|
|
|
|
struct pci_dev **closest_pdevs;
|
|
|
|
int dev_cnt = 0;
|
|
|
|
const int max_devs = PAGE_SIZE / sizeof(*closest_pdevs);
|
|
|
|
int i;
|
|
|
|
|
|
|
|
closest_pdevs = kmalloc(PAGE_SIZE, GFP_KERNEL);
|
|
|
|
if (!closest_pdevs)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev))) {
|
|
|
|
if (!pci_has_p2pmem(pdev))
|
|
|
|
continue;
|
|
|
|
|
|
|
|
distance = pci_p2pdma_distance_many(pdev, clients,
|
|
|
|
num_clients, false);
|
|
|
|
if (distance < 0 || distance > closest_distance)
|
|
|
|
continue;
|
|
|
|
|
|
|
|
if (distance == closest_distance && dev_cnt >= max_devs)
|
|
|
|
continue;
|
|
|
|
|
|
|
|
if (distance < closest_distance) {
|
|
|
|
for (i = 0; i < dev_cnt; i++)
|
|
|
|
pci_dev_put(closest_pdevs[i]);
|
|
|
|
|
|
|
|
dev_cnt = 0;
|
|
|
|
closest_distance = distance;
|
|
|
|
}
|
|
|
|
|
|
|
|
closest_pdevs[dev_cnt++] = pci_dev_get(pdev);
|
|
|
|
}
|
|
|
|
|
|
|
|
if (dev_cnt)
|
|
|
|
pdev = pci_dev_get(closest_pdevs[prandom_u32_max(dev_cnt)]);
|
|
|
|
|
|
|
|
for (i = 0; i < dev_cnt; i++)
|
|
|
|
pci_dev_put(closest_pdevs[i]);
|
|
|
|
|
|
|
|
kfree(closest_pdevs);
|
|
|
|
return pdev;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pmem_find_many);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_alloc_p2p_mem - allocate peer-to-peer DMA memory
|
|
|
|
* @pdev: the device to allocate memory from
|
|
|
|
* @size: number of bytes to allocate
|
|
|
|
*
|
|
|
|
* Returns the allocated memory or NULL on error.
|
|
|
|
*/
|
|
|
|
void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
|
|
|
|
{
|
2019-06-13 16:56:30 -06:00
|
|
|
void *ret = NULL;
|
|
|
|
struct percpu_ref *ref;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
2019-06-13 16:56:30 -06:00
|
|
|
/*
|
|
|
|
* Pairs with synchronize_rcu() in pci_p2pdma_release() to
|
|
|
|
* ensure pdev->p2pdma is non-NULL for the duration of the
|
|
|
|
* read-lock.
|
|
|
|
*/
|
|
|
|
rcu_read_lock();
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
if (unlikely(!pdev->p2pdma))
|
2019-06-13 16:56:30 -06:00
|
|
|
goto out;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
2019-06-13 16:56:30 -06:00
|
|
|
ret = (void *)gen_pool_alloc_owner(pdev->p2pdma->pool, size,
|
|
|
|
(void **) &ref);
|
|
|
|
if (!ret)
|
|
|
|
goto out;
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
|
2019-06-13 16:56:30 -06:00
|
|
|
if (unlikely(!percpu_ref_tryget_live(ref))) {
|
|
|
|
gen_pool_free(pdev->p2pdma->pool, (unsigned long) ret, size);
|
|
|
|
ret = NULL;
|
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
out:
|
|
|
|
rcu_read_unlock();
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_free_p2pmem - free peer-to-peer DMA memory
|
|
|
|
* @pdev: the device the memory was allocated from
|
|
|
|
* @addr: address of the memory that was allocated
|
2018-12-01 10:31:34 -07:00
|
|
|
* @size: number of bytes that were allocated
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
*/
|
|
|
|
void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
|
|
|
|
{
|
2019-06-13 16:56:30 -06:00
|
|
|
struct percpu_ref *ref;
|
|
|
|
|
|
|
|
gen_pool_free_owner(pdev->p2pdma->pool, (uintptr_t)addr, size,
|
|
|
|
(void **) &ref);
|
|
|
|
percpu_ref_put(ref);
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_free_p2pmem);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_virt_to_bus - return the PCI bus address for a given virtual
|
|
|
|
* address obtained with pci_alloc_p2pmem()
|
|
|
|
* @pdev: the device the memory was allocated from
|
|
|
|
* @addr: address of the memory that was allocated
|
|
|
|
*/
|
|
|
|
pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
|
|
|
|
{
|
|
|
|
if (!addr)
|
|
|
|
return 0;
|
|
|
|
if (!pdev->p2pdma)
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Note: when we added the memory to the pool we used the PCI
|
|
|
|
* bus address as the physical address. So gen_pool_virt_to_phys()
|
|
|
|
* actually returns the bus address despite the misleading name.
|
|
|
|
*/
|
|
|
|
return gen_pool_virt_to_phys(pdev->p2pdma->pool, (unsigned long)addr);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist
|
|
|
|
* @pdev: the device to allocate memory from
|
|
|
|
* @nents: the number of SG entries in the list
|
|
|
|
* @length: number of bytes to allocate
|
|
|
|
*
|
2018-12-01 10:31:34 -07:00
|
|
|
* Return: %NULL on error or &struct scatterlist pointer and @nents on success
|
PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
|
|
|
*/
|
|
|
|
struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
|
|
|
|
unsigned int *nents, u32 length)
|
|
|
|
{
|
|
|
|
struct scatterlist *sg;
|
|
|
|
void *addr;
|
|
|
|
|
|
|
|
sg = kzalloc(sizeof(*sg), GFP_KERNEL);
|
|
|
|
if (!sg)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
sg_init_table(sg, 1);
|
|
|
|
|
|
|
|
addr = pci_alloc_p2pmem(pdev, length);
|
|
|
|
if (!addr)
|
|
|
|
goto out_free_sg;
|
|
|
|
|
|
|
|
sg_set_buf(sg, addr, length);
|
|
|
|
*nents = 1;
|
|
|
|
return sg;
|
|
|
|
|
|
|
|
out_free_sg:
|
|
|
|
kfree(sg);
|
|
|
|
return NULL;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()
|
|
|
|
* @pdev: the device to allocate memory from
|
|
|
|
* @sgl: the allocated scatterlist
|
|
|
|
*/
|
|
|
|
void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)
|
|
|
|
{
|
|
|
|
struct scatterlist *sg;
|
|
|
|
int count;
|
|
|
|
|
|
|
|
for_each_sg(sgl, sg, INT_MAX, count) {
|
|
|
|
if (!sg)
|
|
|
|
break;
|
|
|
|
|
|
|
|
pci_free_p2pmem(pdev, sg_virt(sg), sg->length);
|
|
|
|
}
|
|
|
|
kfree(sgl);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
|
|
|
|
|
|
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/**
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* pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by
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* other devices with pci_p2pmem_find()
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* @pdev: the device with peer-to-peer DMA memory to publish
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* @publish: set to true to publish the memory, false to unpublish it
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*
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* Published memory can be used by other PCI device drivers for
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* peer-2-peer DMA operations. Non-published memory is reserved for
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2018-12-01 10:31:34 -07:00
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* exclusive use of the device driver that registers the peer-to-peer
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PCI/P2PDMA: Support peer-to-peer memory
Some PCI devices may have memory mapped in a BAR space that's intended for
use in peer-to-peer transactions. To enable such transactions the memory
must be registered with ZONE_DEVICE pages so it can be used by DMA
interfaces in existing drivers.
Add an interface for other subsystems to find and allocate chunks of P2P
memory as necessary to facilitate transfers between two PCI peers:
struct pci_dev *pci_p2pmem_find[_many]();
int pci_p2pdma_distance[_many]();
void *pci_alloc_p2pmem();
The new interface requires a driver to collect a list of client devices
involved in the transaction then call pci_p2pmem_find() to obtain any
suitable P2P memory. Alternatively, if the caller knows a device which
provides P2P memory, they can use pci_p2pdma_distance() to determine if it
is usable. With a suitable p2pmem device, memory can then be allocated
with pci_alloc_p2pmem() for use in DMA transactions.
Depending on hardware, using peer-to-peer memory may reduce the bandwidth
of the transfer but can significantly reduce pressure on system memory.
This may be desirable in many cases: for example a system could be designed
with a small CPU connected to a PCIe switch by a small number of lanes
which would maximize the number of lanes available to connect to NVMe
devices.
The code is designed to only utilize the p2pmem device if all the devices
involved in a transfer are behind the same PCI bridge. This is because we
have no way of knowing whether peer-to-peer routing between PCIe Root Ports
is supported (PCIe r4.0, sec 1.3.1). Additionally, the benefits of P2P
transfers that go through the RC is limited to only reducing DRAM usage
and, in some cases, coding convenience. The PCI-SIG may be exploring
adding a new capability bit to advertise whether this is possible for
future hardware.
This commit includes significant rework and feedback from Christoph
Hellwig.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: fold in fix from Keith Busch <keith.busch@intel.com>:
https://lore.kernel.org/linux-pci/20181012155920.15418-1-keith.busch@intel.com,
to address comment from Dan Carpenter <dan.carpenter@oracle.com>, fold in
https://lore.kernel.org/linux-pci/20181017160510.17926-1-logang@deltatee.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-10-04 15:27:35 -06:00
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* memory.
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*/
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void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
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{
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if (pdev->p2pdma)
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pdev->p2pdma->p2pmem_published = publish;
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}
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EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
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2018-10-04 15:27:37 -06:00
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/**
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* pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA
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* @dev: device doing the DMA request
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* @sg: scatter list to map
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* @nents: elements in the scatterlist
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* @dir: DMA direction
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*
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* Scatterlists mapped with this function should not be unmapped in any way.
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*
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* Returns the number of SG entries mapped or 0 on error.
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*/
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int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
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enum dma_data_direction dir)
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{
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struct dev_pagemap *pgmap;
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struct scatterlist *s;
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phys_addr_t paddr;
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int i;
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/*
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* p2pdma mappings are not compatible with devices that use
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* dma_virt_ops. If the upper layers do the right thing
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* this should never happen because it will be prevented
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2019-07-02 11:35:44 -06:00
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* by the check in pci_p2pdma_distance_many()
|
2018-10-04 15:27:37 -06:00
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*/
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if (WARN_ON_ONCE(IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
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dev->dma_ops == &dma_virt_ops))
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return 0;
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for_each_sg(sg, s, nents, i) {
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pgmap = sg_page(s)->pgmap;
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paddr = sg_phys(s);
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s->dma_address = paddr - pgmap->pci_p2pdma_bus_offset;
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sg_dma_len(s) = s->length;
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}
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return nents;
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}
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EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg);
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2018-10-04 15:27:38 -06:00
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/**
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* pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
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* to enable p2pdma
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* @page: contents of the value to be stored
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* @p2p_dev: returns the PCI device that was selected to be used
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* (if one was specified in the stored value)
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* @use_p2pdma: returns whether to enable p2pdma or not
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*
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* Parses an attribute value to decide whether to enable p2pdma.
|
2018-12-01 10:31:34 -07:00
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* The value can select a PCI device (using its full BDF device
|
2018-10-04 15:27:38 -06:00
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* name) or a boolean (in any format strtobool() accepts). A false
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* value disables p2pdma, a true value expects the caller
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* to automatically find a compatible device and specifying a PCI device
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* expects the caller to use the specific provider.
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*
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* pci_p2pdma_enable_show() should be used as the show operation for
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|
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* the attribute.
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*
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* Returns 0 on success
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|
*/
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|
|
int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
|
|
|
|
bool *use_p2pdma)
|
|
|
|
{
|
|
|
|
struct device *dev;
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|
|
dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
|
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|
|
if (dev) {
|
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|
|
*use_p2pdma = true;
|
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|
|
*p2p_dev = to_pci_dev(dev);
|
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|
|
if (!pci_has_p2pmem(*p2p_dev)) {
|
|
|
|
pci_err(*p2p_dev,
|
|
|
|
"PCI device has no peer-to-peer memory: %s\n",
|
|
|
|
page);
|
|
|
|
pci_dev_put(*p2p_dev);
|
|
|
|
return -ENODEV;
|
|
|
|
}
|
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|
|
return 0;
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|
|
|
} else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
|
|
|
|
/*
|
|
|
|
* If the user enters a PCI device that doesn't exist
|
|
|
|
* like "0000:01:00.1", we don't want strtobool to think
|
|
|
|
* it's a '0' when it's clearly not what the user wanted.
|
|
|
|
* So we require 0's and 1's to be exactly one character.
|
|
|
|
*/
|
|
|
|
} else if (!strtobool(page, use_p2pdma)) {
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
|
|
|
|
return -ENODEV;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
|
|
|
|
* whether p2pdma is enabled
|
|
|
|
* @page: contents of the stored value
|
|
|
|
* @p2p_dev: the selected p2p device (NULL if no device is selected)
|
2018-12-01 10:31:34 -07:00
|
|
|
* @use_p2pdma: whether p2pdma has been enabled
|
2018-10-04 15:27:38 -06:00
|
|
|
*
|
|
|
|
* Attributes that use pci_p2pdma_enable_store() should use this function
|
|
|
|
* to show the value of the attribute.
|
|
|
|
*
|
|
|
|
* Returns 0 on success
|
|
|
|
*/
|
|
|
|
ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
|
|
|
|
bool use_p2pdma)
|
|
|
|
{
|
|
|
|
if (!use_p2pdma)
|
|
|
|
return sprintf(page, "0\n");
|
|
|
|
|
|
|
|
if (!p2p_dev)
|
|
|
|
return sprintf(page, "1\n");
|
|
|
|
|
|
|
|
return sprintf(page, "%s\n", pci_name(p2p_dev));
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
|