Re: [PATCH v3 1/1] iommu: Allow attaching static domains in iommu_attach_device_pasid()

[Baolu Lu]

On 4/24/25 14:49, Vasant Hegde wrote:
> On 4/24/2025 9:11 AM, Lu Baolu wrote:
> > The idxd driver attaches the default domain to a PASID of the device to
> > perform kernel DMA using that PASID. The domain is attached to the
> > device's PASID through iommu_attach_device_pasid(), which checks if the
> > domain->owner matches the iommu_ops retrieved from the device. If they
> > do not match, it returns a failure.
> >
> >          if (ops != domain->owner || pasid == IOMMU_NO_PASID)
> >                  return -EINVAL;
> >
> > The static identity domain implemented by the intel iommu driver doesn't
> > specify the domain owner. Therefore, kernel DMA with PASID doesn't work
> > for the idxd driver if the device translation mode is set to passthrough.
> >
> > Generally the owner field of static domains are not set because they are
> > already part of iommu ops. Add a helper domain_iommu_ops_compatible()
> > that checks if a domain is compatible with the device's iommu ops. This
> > helper explicitly allows the static blocked and identity domains associated
> > with the device's iommu_ops to be considered compatible.
> >
> > Fixes: 2031c469f816 ("iommu/vt-d: Add support for static identity domain")
> > Closes:https://bugzilla.kernel.org/show_bug.cgi?id=220031
> > Cc:stable@xxxxxxxxxxxxxxx
> > Suggested-by: Jason Gunthorpe<jgg@xxxxxxxxxx>
> > Link:https://lore.kernel.org/linux-iommu/20250422191554.GC1213339@xxxxxxxx/
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > Reviewed-by: Dave Jiang<dave.jiang@xxxxxxxxx>
> > Reviewed-by: Robin Murphy<robin.murphy@xxxxxxx>
>
> Thanks! We have static identity domain in AMD driver as well. Some day we may
> hit similar issue 🙂
>
> Patch looks good to me.
>
> Reviewed-by: Vasant Hegde<vasant.hegde@xxxxxxx>

Thank you!

> W/ this change may be I should fix AMD driver like below. (No need to respin
> patch. I can send topup patch later).

I think that's a cleanup rather than a fix.

Thanks,
baolu