Using __printf attributes helps to detect several format string issues
at compile time (even though -Wformat-security is currently disabled in
Makefile). For example it can detect when formatting a pointer as a
number, like the issue fixed in commit a3fa71c40f ("wl18xx: show
rx_frames_per_rates as an array as it really is"), or when the arguments
do not match the format string, c.f. for example commit 5ce1aca814
("reiserfs: fix __RASSERT format string").
To prevent similar bugs in the future, add a __printf attribute to every
function prototype which needs one in include/linux/ and lib/. These
functions were mostly found by using gcc's -Wsuggest-attribute=format
flag.
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This function can be called by an IOMMU driver to request
that a device's default domain is direct mapped.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Add two new functions to the IOMMU-API to allow the IOMMU
drivers to export the requirements for direct mapped regions
per device.
This is useful for exporting the information in Intel VT-d's
RMRR entries or AMD-Vi's unity mappings.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
All drivers have been converted to the new domain_alloc and
domain_free iommu-ops. So remove the old ones and get rid of
iommu_domain->priv too, as this is no longer needed when the
struct iommu_domain is embedded in the private structures of
the iommu drivers.
Tested-by: Thierry Reding <treding@nvidia.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This allows to handle domains differently based on their
type in the future. An IOMMU driver can implement certain
optimizations for DMA-API domains for example.
The domain types can be extended later and some of the
existing domain attributes can be migrated to become domain
flags.
Tested-by: Thierry Reding <treding@nvidia.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
These new call-backs defer the allocation and destruction of
'struct iommu_domain' to the iommu driver. This allows
drivers to embed this struct into their private domain
structures and to get rid of the domain_init and
domain_destroy call-backs when all drivers have been
converted.
Tested-by: Thierry Reding <treding@nvidia.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
The iomm-config branch contains work from Will Deacon, quoting his description:
This series adds automatic IOMMU and DMA-mapping configuration for
OF-based DMA masters described using the generic IOMMU devicetree
bindings. Although there is plenty of future work around splitting up
iommu_ops, adding default IOMMU domains and sorting out automatic IOMMU
group creation for the platform_bus, this is already useful enough for
people to port over their IOMMU drivers and start using the new probing
infrastructure (indeed, Marek has patches queued for the Exynos IOMMU).
The branch touches core ARM and IOMMU driver files, and the respective
maintainers (Russell King and Joerg Roedel) agreed to have the contents
merged through the arm-soc tree. The final version was ready just before
the merge window, so we ended up delaying it a bit longer than the rest,
but we don't expect to see regressions because this is just additional
infrastructure that will get used in drivers starting in 3.20 but is
unused so far.
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Merge tag 'iommu-config-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
Pull ARM SoC/iommu configuration update from Arnd Bergmann:
"The iomm-config branch contains work from Will Deacon, quoting his
description:
This series adds automatic IOMMU and DMA-mapping configuration for
OF-based DMA masters described using the generic IOMMU devicetree
bindings. Although there is plenty of future work around splitting up
iommu_ops, adding default IOMMU domains and sorting out automatic IOMMU
group creation for the platform_bus, this is already useful enough for
people to port over their IOMMU drivers and start using the new probing
infrastructure (indeed, Marek has patches queued for the Exynos IOMMU).
The branch touches core ARM and IOMMU driver files, and the respective
maintainers (Russell King and Joerg Roedel) agreed to have the
contents merged through the arm-soc tree.
The final version was ready just before the merge window, so we ended
up delaying it a bit longer than the rest, but we don't expect to see
regressions because this is just additional infrastructure that will
get used in drivers starting in 3.20 but is unused so far"
* tag 'iommu-config-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
iommu: store DT-probed IOMMU data privately
arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops
arm: call iommu_init before of_platform_populate
dma-mapping: detect and configure IOMMU in of_dma_configure
iommu: fix initialization without 'add_device' callback
iommu: provide helper function to configure an IOMMU for an of master
iommu: add new iommu_ops callback for adding an OF device
dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops
iommu: provide early initialisation hook for IOMMU drivers
This patch adds a new function to the iommu_ops structure to allow an
OF device to be added to a specific IOMMU instance using the recently
merged generic devicetree binding for IOMMUs. The callback (of_xlate)
takes a struct device representing the master and an of_phandle_args
representing the IOMMU and the correspondong IDs for the new master.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
IOMMU drivers must be initialised before any of their upstream devices,
otherwise the relevant iommu_ops won't be configured for the bus in
question. To solve this, a number of IOMMU drivers use initcalls to
initialise the driver before anything has a chance to be probed.
Whilst this solves the immediate problem, it leaves the job of probing
the IOMMU completely separate from the iommu_ops to configure the IOMMU,
which are called on a per-bus basis and require the driver to figure out
exactly which instance of the IOMMU is being requested. In particular,
the add_device callback simply passes a struct device to the driver,
which then has to parse firmware tables or probe buses to identify the
relevant IOMMU instance.
This patch takes the first step in addressing this problem by adding an
early initialisation pass for IOMMU drivers, giving them the ability to
store some per-instance data in their iommu_ops structure and store that
in their of_node. This can later be used when parsing OF masters to
identify the IOMMU instance in question.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Some IOMMUs accept an IOMMU_NOEXEC protection flag in addition to
IOMMU_READ and IOMMU_WRITE. Expose this as an IOMMU capability.
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Exposing the XN flag of the SMMU driver as IOMMU_NOEXEC instead of
IOMMU_EXEC makes it enforceable, since for IOMMUs that don't support
the XN flag pages will always be executable.
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Mapping and unmapping are more often than not in the critical path.
map_sg allows IOMMU driver implementations to optimize the process
of mapping buffers into the IOMMU page tables.
Instead of mapping a buffer one page at a time and requiring potentially
expensive TLB operations for each page, this function allows the driver
to map all pages in one go and defer TLB maintenance until after all
pages have been mapped.
Additionally, the mapping operation would be faster in general since
clients does not have to keep calling map API over and over again for
each physically contiguous chunk of memory that needs to be mapped to a
virtually contiguous region.
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This pull-request includes:
* Change in the IOMMU-API to convert the former iommu_domain_capable
function to just iommu_capable
* Various fixes in handling RMRR ranges for the VT-d driver (one fix
requires a device driver core change which was acked
by Greg KH)
* The AMD IOMMU driver now assigns and deassigns complete alias groups
to fix issues with devices using the wrong PCI request-id
* MMU-401 support for the ARM SMMU driver
* Multi-master IOMMU group support for the ARM SMMU driver
* Various other small fixes all over the place
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Merge tag 'iommu-updates-v3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu
Pull IOMMU updates from Joerg Roedel:
"This pull-request includes:
- change in the IOMMU-API to convert the former iommu_domain_capable
function to just iommu_capable
- various fixes in handling RMRR ranges for the VT-d driver (one fix
requires a device driver core change which was acked by Greg KH)
- the AMD IOMMU driver now assigns and deassigns complete alias
groups to fix issues with devices using the wrong PCI request-id
- MMU-401 support for the ARM SMMU driver
- multi-master IOMMU group support for the ARM SMMU driver
- various other small fixes all over the place"
* tag 'iommu-updates-v3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu: (41 commits)
iommu/vt-d: Work around broken RMRR firmware entries
iommu/vt-d: Store bus information in RMRR PCI device path
iommu/vt-d: Only remove domain when device is removed
driver core: Add BUS_NOTIFY_REMOVED_DEVICE event
iommu/amd: Fix devid mapping for ivrs_ioapic override
iommu/irq_remapping: Fix the regression of hpet irq remapping
iommu: Fix bus notifier breakage
iommu/amd: Split init_iommu_group() from iommu_init_device()
iommu: Rework iommu_group_get_for_pci_dev()
iommu: Make of_device_id array const
amd_iommu: do not dereference a NULL pointer address.
iommu/omap: Remove omap_iommu unused owner field
iommu: Remove iommu_domain_has_cap() API function
IB/usnic: Convert to use new iommu_capable() API function
vfio: Convert to use new iommu_capable() API function
kvm: iommu: Convert to use new iommu_capable() API function
iommu/tegra: Convert to iommu_capable() API function
iommu/msm: Convert to iommu_capable() API function
iommu/vt-d: Convert to iommu_capable() API function
iommu/fsl: Convert to iommu_capable() API function
...
Some IOMMUs, such as the ARM SMMU, support two stages of translation.
The idea behind such a scheme is to allow a guest operating system to
use the IOMMU for DMA mappings in the first stage of translation, with
the hypervisor then installing mappings in the second stage to provide
isolation of the DMA to the physical range assigned to that virtual
machine.
In order to allow IOMMU domains to be used for second-stage translation,
this patch adds a new iommu_attr (IOMMU_ATTR_NESTING) for setting
second-stage domains prior to device attach. The attribute can also be
queried to see if a domain is actually making use of nesting.
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This function will replace the current iommu_domain_has_cap
function and clean up the interface while at it.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
0-day kernel build testing reports:
arch/x86/kvm/x86.o: In function `iommu_device_destroy':
>> (.text+0x7a0a): multiple definition of `iommu_device_destroy'
arch/x86/kvm/../../../virt/kvm/vfio.o:vfio.c:(.text+0x490): first defined here
arch/x86/kvm/x86.o: In function `iommu_device_link':
>> (.text+0x7a15): multiple definition of `iommu_device_link'
arch/x86/kvm/../../../virt/kvm/vfio.o:vfio.c:(.text+0x49b): first defined here
arch/x86/kvm/x86.o: In function `iommu_device_unlink':
>> (.text+0x7a25): multiple definition of `iommu_device_unlink'
arch/x86/kvm/../../../virt/kvm/vfio.o:vfio.c:(.text+0x4ab): first defined here
arch/x86/kvm/x86.o: In function `iommu_device_create':
>> (.text+0x79f8): multiple definition of `iommu_device_create'
arch/x86/kvm/../../../virt/kvm/vfio.o:vfio.c:(.text+0x47e): first defined here
These are due to failing to define the stubs as static inline. Fix.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This structure is read-only data and should never be modified.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
IOMMUs currently have no common representation to userspace, most
seem to have no representation at all aside from a few printks
on bootup. There are however features of IOMMUs that are useful
to know about. For instance the IOMMU might support superpages,
making use of processor large/huge pages more important in a device
assignment scenario. It's also useful to create cross links between
devices and IOMMU hardware units, so that users might be able to
load balance their devices to avoid thrashing a single hardware unit.
This patch adds a device create and destroy interface as well as
device linking, making it very lightweight for an IOMMU driver to add
basic support. IOMMU drivers can provide additional attributes
automatically by using an attribute_group.
The attributes exposed are expected to be relatively device specific,
the means to retrieve them certainly are, so there are currently no
common attributes for the new class created here.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Currently each IOMMU driver that supports IOMMU groups has its own
code for discovering the base device used in grouping. This code
is generally not specific to the IOMMU hardware, but to the bus of
the devices managed by the IOMMU. We can therefore create a common
interface for supporting devices on different buses.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
domain_has_cap is a misnomer bc the func name should be
the same for CONFIG_IOMMU_API and !CONFIG_IOMMU_API.
Signed-off-by: Upinder Malhi <umalhi@cisco.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Almost every function in include/linux/iommu.h has an empty stub
but the iommu_group_get_by_id() did not get one by mistake.
This adds an empty stub for iommu_group_get_by_id() for IOMMU_API
disabled config.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Whilst most IOMMU mappings should probably be non-executable, there
may be cases (HSA?) where executable mappings are required.
This patch introduces a new mapping flag, IOMMU_EXEC, to indicate that
the mapping should be mapped as executable.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Change iommu driver call io_page_fault trace event. This iommu_error class
event can be enabled to trigger when an iommu error occurs. Trace information
includes driver name, device name, iova, and flags.
Testing:
Added trace calls to iommu_prepare_identity_map() for testing some of the
conditions that are hard to trigger. Here is the trace from the testing:
swapper/0-1 [003] .... 2.003774: io_page_fault: IOMMU:pci 0000:00:02.0 iova=0x00000000cb800000 flags=0x0002
swapper/0-1 [003] .... 2.004098: io_page_fault: IOMMU:pci 0000:00:1d.0 iova=0x00000000cadc6000 flags=0x0002
swapper/0-1 [003] .... 2.004115: io_page_fault: IOMMU:pci 0000:00:1a.0 iova=0x00000000cadc6000 flags=0x0002
swapper/0-1 [003] .... 2.004129: io_page_fault: IOMMU:pci 0000:00:1f.0 iova=0x0000000000000000 flags=0x0002
Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Added the following domain attributes for the FSL PAMU driver:
1. Added new iommu stash attribute, which allows setting of the
LIODN specific stash id parameter through IOMMU API.
2. Added an attribute for enabling/disabling DMA to a particular
memory window.
3. Added domain attribute to check for PAMUV1 specific constraints.
Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
As IOMMU groups are exposed to the user space by their numbers,
the user space can use them in various kernel APIs so the kernel
might need an API to find a group by its ID.
As an example, QEMU VFIO on PPC64 platform needs it to associate
a logical bus number (LIOBN) with a specific IOMMU group in order
to support in-kernel handling of DMA map/unmap requests.
The patch adds the iommu_group_get_by_id(id) function which performs
such search.
v2: fixed reference counting.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
The linux/iommu.h header uses ERR_PTR defined
in linux/err.h but doesn't include it.
Cc:joro@8bytes.org
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Each iommu window can have access permissions associated with it. Extended the
window_enable API to incorporate window access permissions.
In case of PAMU each window can have its specific set of permissions.
Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
This is required in case of PAMU, as it can support a window size of up
to 64G (even on 32bit).
Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Add the iommu_domain_window_enable() and iommu_domain_window_disable()
functions to the IOMMU-API. These functions will be used to setup
domains that are based on subwindows and not on paging.
Signed-off-by: Joerg Roedel <joro@8bytes.org>
This attribute of a domain can be queried to find out if the
domain supports setting up page-tables using the iommu_map()
and iommu_unmap() functions.
Signed-off-by: Joerg Roedel <joro@8bytes.org>
The 'struct notifier_block' is not used in linux/iommu.h but
not declared anywhere. Add a forward declaration for it.
Reported-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
The linux/iommu.h header uses types defined in linux/types.h but doesn't
include it.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This patch introduces an extension to the iommu-api to get
and set attributes for an iommu_domain. Two functions are
introduced for this:
* iommu_domain_get_attr()
* iommu_domain_set_attr()
These functions will be used to make the iommu-api suitable
for GART-like IOMMUs and to implement hardware-specifc
api-extensions.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
IOMMU device groups are currently a rather vague associative notion
with assembly required by the user or user level driver provider to
do anything useful. This patch intends to grow the IOMMU group concept
into something a bit more consumable.
To do this, we first create an object representing the group, struct
iommu_group. This structure is allocated (iommu_group_alloc) and
filled (iommu_group_add_device) by the iommu driver. The iommu driver
is free to add devices to the group using it's own set of policies.
This allows inclusion of devices based on physical hardware or topology
limitations of the platform, as well as soft requirements, such as
multi-function trust levels or peer-to-peer protection of the
interconnects. Each device may only belong to a single iommu group,
which is linked from struct device.iommu_group. IOMMU groups are
maintained using kobject reference counting, allowing for automatic
removal of empty, unreferenced groups. It is the responsibility of
the iommu driver to remove devices from the group
(iommu_group_remove_device).
IOMMU groups also include a userspace representation in sysfs under
/sys/kernel/iommu_groups. When allocated, each group is given a
dynamically assign ID (int). The ID is managed by the core IOMMU group
code to support multiple heterogeneous iommu drivers, which could
potentially collide in group naming/numbering. This also keeps group
IDs to small, easily managed values. A directory is created under
/sys/kernel/iommu_groups for each group. A further subdirectory named
"devices" contains links to each device within the group. The iommu_group
file in the device's sysfs directory, which formerly contained a group
number when read, is now a link to the iommu group. Example:
$ ls -l /sys/kernel/iommu_groups/26/devices/
total 0
lrwxrwxrwx. 1 root root 0 Apr 17 12:57 0000:00:1e.0 ->
../../../../devices/pci0000:00/0000:00:1e.0
lrwxrwxrwx. 1 root root 0 Apr 17 12:57 0000:06:0d.0 ->
../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.0
lrwxrwxrwx. 1 root root 0 Apr 17 12:57 0000:06:0d.1 ->
../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.1
$ ls -l /sys/kernel/iommu_groups/26/devices/*/iommu_group
[truncating perms/owner/timestamp]
/sys/kernel/iommu_groups/26/devices/0000:00:1e.0/iommu_group ->
../../../kernel/iommu_groups/26
/sys/kernel/iommu_groups/26/devices/0000:06:0d.0/iommu_group ->
../../../../kernel/iommu_groups/26
/sys/kernel/iommu_groups/26/devices/0000:06:0d.1/iommu_group ->
../../../../kernel/iommu_groups/26
Groups also include several exported functions for use by user level
driver providers, for example VFIO. These include:
iommu_group_get(): Acquires a reference to a group from a device
iommu_group_put(): Releases reference
iommu_group_for_each_dev(): Iterates over group devices using callback
iommu_group_[un]register_notifier(): Allows notification of device add
and remove operations relevant to the group
iommu_group_id(): Return the group number
This patch also extends the IOMMU API to allow attaching groups to
domains. This is currently a simple wrapper for iterating through
devices within a group, but it's expected that the IOMMU API may
eventually make groups a more integral part of domains.
Groups intentionally do not try to manage group ownership. A user
level driver provider must independently acquire ownership for each
device within a group before making use of the group as a whole.
This may change in the future if group usage becomes more pervasive
across both DMA and IOMMU ops.
Groups intentionally do not provide a mechanism for driver locking
or otherwise manipulating driver matching/probing of devices within
the group. Such interfaces are generic to devices and beyond the
scope of IOMMU groups. If implemented, user level providers have
ready access via iommu_group_for_each_dev and group notifiers.
iommu_device_group() is removed here as it has no users. The
replacement is:
group = iommu_group_get(dev);
id = iommu_group_id(group);
iommu_group_put(group);
AMD-Vi & Intel VT-d support re-added in following patches.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Sometimes a single IOMMU user may have to deal with several
different IOMMU devices (e.g. remoteproc).
When an IOMMU fault happens, such users have to regain their
context in order to deal with the fault.
Users can't use the private fields of neither the iommu_domain nor
the IOMMU device, because those are already used by the IOMMU core
and low level driver (respectively).
This patch just simply allows users to pass a private token (most
notably their own context pointer) to iommu_set_fault_handler(),
and then makes sure it is provided back to the users whenever
an IOMMU fault happens.
The patch also adopts remoteproc to the new fault handling
interface, but the real functionality using this (recovery of
remote processors) will only be added later in a subsequent patch
set.
Cc: Fernando Guzman Lugo <fernando.lugo@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
An IOMMU group is a set of devices for which the IOMMU cannot
distinguish transactions. For PCI devices, a group often occurs
when a PCI bridge is involved. Transactions from any device
behind the bridge appear to be sourced from the bridge itself.
We leave it to the IOMMU driver to define the grouping restraints
for their platform.
Using this new interface, the group for a device can be retrieved
using the iommu_device_group() callback. Users will compare the
value returned against the value returned for other devices to
determine whether they are part of the same group. Devices with
no group are not translated by the IOMMU. There should be no
expectations about the group numbers as they may be arbitrarily
assigned by the IOMMU driver and may not be persistent across boots.
We also provide a sysfs interface to the group numbers here so
that userspace can understand IOMMU dependencies between devices
for managing safe, userspace drivers.
[Some code changes by Joerg Roedel <joerg.roedel@amd.com>]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
