> From: Lu Baolu <baolu...@linux.intel.com>
> Sent: Thursday, April 21, 2022 7:36 PM
>
> 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...@linux.intel.com>
> Reviewed-by: Jacob Pan <jacob.jun....@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.t...@intel.com>
> ---
> drivers/iommu/intel/svm.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index c720d1be992d..0741ec165673 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -760,6 +760,10 @@ static irqreturn_t prq_event_thread(int irq, void *d)
> 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
> --
> 2.25.1
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