iommu/vt-d: Drop stop marker messages

commit da8669ff41fa31573375c9a4180f5c080677204b upstream.

The page fault handling framework in the IOMMU core explicitly states
that it doesn't handle PCI PASID Stop Marker and the IOMMU drivers must
discard them before reporting faults. This handles Stop Marker messages
in prq_event_thread() before reporting events to the core.

The VT-d driver explicitly drains the pending page requests when a CPU
page table (represented by a mm struct) is unbound from a PASID according
to the procedures defined in the VT-d spec. The Stop Marker messages do
not need a response. Hence, it is safe to drop the Stop Marker messages
silently if any of them is found in the page request queue.

Fixes: d5b9e4bfe0d88 ("iommu/vt-d: Report prq to io-pgfault framework")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20220421113558.3504874-1-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20220423082330.3897867-2-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 0c228787704f36a68e5503db7330e813af4b1dac..3a9468b1d2c3c217ec2efc19258aaaf644517c44 100644 (file)
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -978,6 +978,10 @@ bad_req:
                        goto bad_req;
                }
 
+               /* Drop Stop Marker message. No need for a response. */
+               if (unlikely(req->lpig && !req->rd_req && !req->wr_req))
+                       goto prq_advance;
+
                if (!svm || svm->pasid != req->pasid) {
                        /*
                         * It can't go away, because the driver is not permitted