Re: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure

[Baolu Lu]

On 2022/6/20 16:31, Yi Liu wrote:
> Hi Baolu,
>
> On 2022/6/20 16:17, Lu Baolu wrote:
> > The IOMMU driver shares the pasid table for PCI alias devices. When the
> > RID2PASID entry of the shared pasid table has been filled by the first
> > device, the subsequent devices will encounter the "DMAR: Setup RID2PASID
> > failed" failure as the pasid entry has already been marke as present. As
>
> s/marke/marked/

Updated. Thanks!

> > the result, the IOMMU probing process will be aborted.
> >
> > This fixes it by skipping RID2PASID setting if the pasid entry has been
> > populated. This works because the IOMMU core ensures that only the same
> > IOMMU domain can be attached to all PCI alias devices at the same time.
>
> nit. this sentence is a little bit to interpret. :-) I guess what you want
> to describe is the PCI alias devices should be attached to the same domain
> instead of different domain. right?

Yes.

> also, does it apply to all domain types? e.g. the SVA domains introduced 
> in "iommu: SVA and IOPF refactoring"

No. Only about the RID2PASID.

> > Therefore the subsequent devices just try to setup the RID2PASID entry
> > with the same domain, which is negligible.
> >
> > Fixes: ef848b7e5a6a0 ("iommu/vt-d: Setup pasid entry for RID2PASID 
> > support")
> > Reported-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 44016594831d..b9966c01a2a2 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -2564,7 +2564,7 @@ static int domain_add_dev_info(struct 
> > dmar_domain *domain, struct device *dev)
> >               ret = intel_pasid_setup_second_level(iommu, domain,
> >                       dev, PASID_RID2PASID);
> >           spin_unlock_irqrestore(&iommu->lock, flags);
> > -        if (ret) {
> > +        if (ret && ret != -EBUSY) {
> >               dev_err(dev, "Setup RID2PASID failed\n");
> >               dmar_remove_one_dev_info(dev);
> >               return ret;

--
Best regards,
baolu