[ Upstream commit 3cf74230c139f208b7fb313ae0054386eee31a81 ]
If qi_submit_sync() is invoked with 0 invalidation descriptors (for
instance, for DMA draining purposes), we can run into a bug where a
submitting thread fails to detect the completion of invalidation_wait.
Subsequently, this led to a soft lockup. Currently, there is no impact
by this bug on the existing users because no callers are submitting
invalidations with 0 descriptors. This fix will enable future users
(such as DMA drain) calling qi_submit_sync() with 0 count.
Suppose thread T1 invokes qi_submit_sync() with non-zero descriptors, while
concurrently, thread T2 calls qi_submit_sync() with zero descriptors. Both
threads then enter a while loop, waiting for their respective descriptors
to complete. T1 detects its completion (i.e., T1's invalidation_wait status
changes to QI_DONE by HW) and proceeds to call reclaim_free_desc() to
reclaim all descriptors, potentially including adjacent ones of other
threads that are also marked as QI_DONE.
During this time, while T2 is waiting to acquire the qi->q_lock, the IOMMU
hardware may complete the invalidation for T2, setting its status to
QI_DONE. However, if T1's execution of reclaim_free_desc() frees T2's
invalidation_wait descriptor and changes its status to QI_FREE, T2 will
not observe the QI_DONE status for its invalidation_wait and will
indefinitely remain stuck.
This soft lockup does not occur when only non-zero descriptors are
submitted.In such cases, invalidation descriptors are interspersed among
wait descriptors with the status QI_IN_USE, acting as barriers. These
barriers prevent the reclaim code from mistakenly freeing descriptors
belonging to other submitters.
Considered the following example timeline:
T1 T2
========================================
ID1
WD1
while(WD1!=QI_DONE)
unlock
lock
WD1=QI_DONE* WD2
while(WD2!=QI_DONE)
unlock
lock
WD1==QI_DONE?
ID1=QI_DONE WD2=DONE*
reclaim()
ID1=FREE
WD1=FREE
WD2=FREE
unlock
soft lockup! T2 never sees QI_DONE in WD2
Where:
ID = invalidation descriptor
WD = wait descriptor
* Written by hardware
The root of the problem is that the descriptor status QI_DONE flag is used
for two conflicting purposes:
1. signal a descriptor is ready for reclaim (to be freed)
2. signal by the hardware that a wait descriptor is complete
The solution (in this patch) is state separation by using QI_FREE flag
for #1.
Once a thread's invalidation descriptors are complete, their status would
be set to QI_FREE. The reclaim_free_desc() function would then only
free descriptors marked as QI_FREE instead of those marked as
QI_DONE. This change ensures that T2 (from the previous example) will
correctly observe the completion of its invalidation_wait (marked as
QI_DONE).
Signed-off-by: Sanjay K Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240728210059.1964602-1-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 2c13012e09190174614fd6901857a1b8c199e17d ]
We will use a global static identity domain. Reserve a static domain ID
for it.
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Link: https://lore.kernel.org/r/20240809055431.36513-4-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit b5e86a95541cea737394a1da967df4cd4d8f7182 ]
Queued invalidation wait descriptor status is volatile in that IOMMU
hardware writes the data upon completion.
Use READ_ONCE() to prevent compiler optimizations which ensures memory
reads every time. As a side effect, READ_ONCE() also enforces strict
types and may add an extra instruction. But it should not have negative
performance impact since we use cpu_relax anyway and the extra time(by
adding an instruction) may allow IOMMU HW request cacheline ownership
easier.
e.g. gcc 12.3
BEFORE:
81 38 ad de 00 00 cmpl $0x2,(%rax)
AFTER (with READ_ONCE())
772f: 8b 00 mov (%rax),%eax
7731: 3d ad de 00 00 cmp $0x2,%eax
//status data is 32 bit
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20240607173817.3914600-1-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20240702130839.108139-2-baolu.lu@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit a34f3e20ddff02c4f12df2c0635367394e64c63d ]
The page request queue is per IOMMU, its allocation should be made
NUMA-aware for performance reasons.
Fixes: a222a7f0bb6c ("iommu/vt-d: Implement page request handling")
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240403214007.985600-1-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 85b80fdffa867d75dfb9084a839e7949e29064e8 upstream.
The VT-d spec requires (10.4.4 Global Command Register, TE field) that:
Hardware implementations supporting DMA draining must drain any in-flight
DMA read/write requests queued within the Root-Complex before switching
address translation on or off and reflecting the status of the command
through the TES field in the Global Status register.
Unfortunately, some integrated graphic devices fail to do so after some
kind of power state transition. As the result, the system might stuck in
iommu_disable_translation(), waiting for the completion of TE transition.
Add MTL to the quirk list for those devices and skips TE disabling if the
qurik hits.
Fixes: b1012ca8dc4f ("iommu/vt-d: Skip TE disabling on quirky gfx dedicated iommu")
Cc: stable@vger.kernel.org
Signed-off-by: Abdul Halim, Mohd Syazwan <mohd.syazwan.abdul.halim@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20231116022324.30120-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
