Re: [PATCH 1/1] iommu/vt-d: Draining PRQ in sva unbind path when FPD bit set

[Baolu Lu]

On 2024/12/17 15:39, Tian, Kevin wrote:
> > From: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Tuesday, December 17, 2024 10:43 AM
> >
> > When a device uses a PASID for SVA (Shared Virtual Address), it's possible
> > that the PASID entry is marked as non-present and FPD bit set before the
> > device flushes all ongoing DMA requests and removes the SVA domain. This
> > can occur when an exception happens and the process terminates before the
> > device driver stops DMA and calls the iommu driver to unbind the PASID.
> >
> > There's no need to drain the PRQ in the mm release path. Instead, the PRQ
> > will be drained in the SVA unbind path. But in such case,
> > intel_pasid_tear_down_entry() only checks the presence of the pasid entry
> > and returns directly.
> >
> > Add the code to clear the FPD bit and drain the PRQ.
> >
> > Suggested-by: Kevin Tian<kevin.tian@xxxxxxxxx>
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> Need a fix tag given the old code doesn't work correctly?

Yes.

Fixes: c43e1ccdebf2 ("iommu/vt-d: Drain PRQs when domain removed from RID")