Re: [PATCH v2 3/4] iommu/vt-d: Drop stop marker messages
On 2022/4/22 11:05, Tian, Kevin wrote:
From: Lu Baolu
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
Reviewed-by: Jacob Pan
Reviewed-by: Kevin Tian
Thank you, Kevin. I will queue this patch to Joerg as a fix for v5.18.
Best regards,
baolu
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RE: [PATCH v2 3/4] iommu/vt-d: Drop stop marker messages
> From: Lu Baolu
> 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
> Reviewed-by: Jacob Pan
Reviewed-by: Kevin Tian
> ---
> 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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[PATCH v2 3/4] iommu/vt-d: Drop stop marker messages
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
Reviewed-by: Jacob Pan
---
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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