set dmar->iommu_superpage field to the smallest common denominator
of super page sizes supported by all active VT-d engines. Initialize
this field in intel_iommu_domain_init() API so intel_iommu_map() API
will be able to use iommu_superpage field to determine the appropriate
super page size to use.
Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
iommu_unmap() API expects IOMMU drivers to return the actual page order
of the address being unmapped. Previous code was just returning page
order passed in from the caller. This patch fixes this problem.
Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
We really don't want this to work in the general case; device drivers
*shouldn't* care whether they are behind an IOMMU or not. But the
integrated graphics is a special case, because the IOMMU and the GTT are
all kind of smashed into one and generally horrifically buggy, so it's
reasonable for the graphics driver to want to know when the IOMMU is
active for the graphics hardware.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
To work around a hardware issue, we have to submit IOTLB flushes while
the graphics engine is idle. The graphics driver will (we hope) go to
great lengths to ensure that it gets that right on the affected
chipset(s)... so let's not screw it over by deferring the unmap and
doing it later. That wouldn't be very helpful.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
When unbinding a device so that I could pass it through to a KVM VM, I
got the lockdep report below. It looks like a legitimate lock
ordering problem:
- domain_context_mapping_one() takes iommu->lock and calls
iommu_support_dev_iotlb(), which takes device_domain_lock (inside
iommu->lock).
- domain_remove_one_dev_info() starts by taking device_domain_lock
then takes iommu->lock inside it (near the end of the function).
So this is the classic AB-BA deadlock. It looks like a safe fix is to
simply release device_domain_lock a bit earlier, since as far as I can
tell, it doesn't protect any of the stuff accessed at the end of
domain_remove_one_dev_info() anyway.
BTW, the use of device_domain_lock looks a bit unsafe to me... it's
at least not obvious to me why we aren't vulnerable to the race below:
iommu_support_dev_iotlb()
domain_remove_dev_info()
lock device_domain_lock
find info
unlock device_domain_lock
lock device_domain_lock
find same info
unlock device_domain_lock
free_devinfo_mem(info)
do stuff with info after it's free
However I don't understand the locking here well enough to know if
this is a real problem, let alone what the best fix is.
Anyway here's the full lockdep output that prompted all of this:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.39.1+ #1
-------------------------------------------------------
bash/13954 is trying to acquire lock:
(&(&iommu->lock)->rlock){......}, at: [<ffffffff812f6421>] domain_remove_one_dev_info+0x121/0x230
but task is already holding lock:
(device_domain_lock){-.-...}, at: [<ffffffff812f6508>] domain_remove_one_dev_info+0x208/0x230
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (device_domain_lock){-.-...}:
[<ffffffff8109ca9d>] lock_acquire+0x9d/0x130
[<ffffffff81571475>] _raw_spin_lock_irqsave+0x55/0xa0
[<ffffffff812f8350>] domain_context_mapping_one+0x600/0x750
[<ffffffff812f84df>] domain_context_mapping+0x3f/0x120
[<ffffffff812f9175>] iommu_prepare_identity_map+0x1c5/0x1e0
[<ffffffff81ccf1ca>] intel_iommu_init+0x88e/0xb5e
[<ffffffff81cab204>] pci_iommu_init+0x16/0x41
[<ffffffff81002165>] do_one_initcall+0x45/0x190
[<ffffffff81ca3d3f>] kernel_init+0xe3/0x168
[<ffffffff8157ac24>] kernel_thread_helper+0x4/0x10
-> #0 (&(&iommu->lock)->rlock){......}:
[<ffffffff8109bf3e>] __lock_acquire+0x195e/0x1e10
[<ffffffff8109ca9d>] lock_acquire+0x9d/0x130
[<ffffffff81571475>] _raw_spin_lock_irqsave+0x55/0xa0
[<ffffffff812f6421>] domain_remove_one_dev_info+0x121/0x230
[<ffffffff812f8b42>] device_notifier+0x72/0x90
[<ffffffff8157555c>] notifier_call_chain+0x8c/0xc0
[<ffffffff81089768>] __blocking_notifier_call_chain+0x78/0xb0
[<ffffffff810897b6>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff81373a5c>] __device_release_driver+0xbc/0xe0
[<ffffffff81373ccf>] device_release_driver+0x2f/0x50
[<ffffffff81372ee3>] driver_unbind+0xa3/0xc0
[<ffffffff813724ac>] drv_attr_store+0x2c/0x30
[<ffffffff811e4506>] sysfs_write_file+0xe6/0x170
[<ffffffff8117569e>] vfs_write+0xce/0x190
[<ffffffff811759e4>] sys_write+0x54/0xa0
[<ffffffff81579a82>] system_call_fastpath+0x16/0x1b
other info that might help us debug this:
6 locks held by bash/13954:
#0: (&buffer->mutex){+.+.+.}, at: [<ffffffff811e4464>] sysfs_write_file+0x44/0x170
#1: (s_active#3){++++.+}, at: [<ffffffff811e44ed>] sysfs_write_file+0xcd/0x170
#2: (&__lockdep_no_validate__){+.+.+.}, at: [<ffffffff81372edb>] driver_unbind+0x9b/0xc0
#3: (&__lockdep_no_validate__){+.+.+.}, at: [<ffffffff81373cc7>] device_release_driver+0x27/0x50
#4: (&(&priv->bus_notifier)->rwsem){.+.+.+}, at: [<ffffffff8108974f>] __blocking_notifier_call_chain+0x5f/0xb0
#5: (device_domain_lock){-.-...}, at: [<ffffffff812f6508>] domain_remove_one_dev_info+0x208/0x230
stack backtrace:
Pid: 13954, comm: bash Not tainted 2.6.39.1+ #1
Call Trace:
[<ffffffff810993a7>] print_circular_bug+0xf7/0x100
[<ffffffff8109bf3e>] __lock_acquire+0x195e/0x1e10
[<ffffffff810972bd>] ? trace_hardirqs_off+0xd/0x10
[<ffffffff8109d57d>] ? trace_hardirqs_on_caller+0x13d/0x180
[<ffffffff8109ca9d>] lock_acquire+0x9d/0x130
[<ffffffff812f6421>] ? domain_remove_one_dev_info+0x121/0x230
[<ffffffff81571475>] _raw_spin_lock_irqsave+0x55/0xa0
[<ffffffff812f6421>] ? domain_remove_one_dev_info+0x121/0x230
[<ffffffff810972bd>] ? trace_hardirqs_off+0xd/0x10
[<ffffffff812f6421>] domain_remove_one_dev_info+0x121/0x230
[<ffffffff812f8b42>] device_notifier+0x72/0x90
[<ffffffff8157555c>] notifier_call_chain+0x8c/0xc0
[<ffffffff81089768>] __blocking_notifier_call_chain+0x78/0xb0
[<ffffffff810897b6>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff81373a5c>] __device_release_driver+0xbc/0xe0
[<ffffffff81373ccf>] device_release_driver+0x2f/0x50
[<ffffffff81372ee3>] driver_unbind+0xa3/0xc0
[<ffffffff813724ac>] drv_attr_store+0x2c/0x30
[<ffffffff811e4506>] sysfs_write_file+0xe6/0x170
[<ffffffff8117569e>] vfs_write+0xce/0x190
[<ffffffff811759e4>] sys_write+0x54/0xa0
[<ffffffff81579a82>] system_call_fastpath+0x16/0x1b
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This should ease finding similarities with different platforms,
with the intention of solving problems once in a generic framework
which everyone can use.
Note: to move intel-iommu.c, the declaration of pci_find_upstream_pcie_bridge()
has to move from drivers/pci/pci.h to include/linux/pci.h. This is handled
in this patch, too.
As suggested, also drop DMAR's EXPERIMENTAL tag while we're at it.
Compile-tested on x86_64.
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
