Re: [PATCH v9 10/11] iommu: Per-domain I/O page fault handling

[Baolu Lu]

On 2022/6/28 18:02, Tian, Kevin wrote:
> > From: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > Sent: Tuesday, June 28, 2022 5:44 PM
> >
> > On Tue, Jun 28, 2022 at 08:39:36AM +0000, Tian, Kevin wrote:
> > > > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > > > Sent: Tuesday, June 21, 2022 10:44 PM
> > > >
> > > > Tweak the I/O page fault handling framework to route the page faults to
> > > > the domain and call the page fault handler retrieved from the domain.
> > > > This makes the I/O page fault handling framework possible to serve more
> > > > usage scenarios as long as they have an IOMMU domain and install a
> > page
> > > > fault handler in it. Some unused functions are also removed to avoid
> > > > dead code.
> > > >
> > > > The iommu_get_domain_for_dev_pasid() which retrieves attached
> > domain
> > > > for a {device, PASID} pair is used. It will be used by the page fault
> > > > handling framework which knows {device, PASID} reported from the
> > iommu
> > > > driver. We have a guarantee that the SVA domain doesn't go away during
> > > > IOPF handling, because unbind() waits for pending faults with
> > > > iopf_queue_flush_dev() before freeing the domain. Hence, there's no
> > need
> > > > to synchronize life cycle of the iommu domains between the unbind() and
> > > > the interrupt threads.
> > >
> > > I found iopf_queue_flush_dev() is only called in intel-iommu driver. Did
> > > I overlook anything?
> >
> > The SMMU driver will need it as well when we upstream PRI support.
> > Currently it only supports stall, and that requires the device driver to
> > flush all DMA including stalled transactions *before* calling unbind(), so
> > ne need for iopf_queue_flush_dev() in this case.
>
> then it makes sense. Probably Baolu can add this information in the
> commit msg so others with similar question can quickly get the
> point here.

Sure. Updated.

Best regards,
baolu