Re: [PATCH 1/3] iommu/vt-d: Set PGSNP bit in pasid table entry for sva binding

[Lu Baolu]

On 2022/4/18 14:56, Tian, Kevin wrote:
> > From: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Saturday, April 16, 2022 8:31 PM
> >
> > This field make the requests snoop processor caches irrespective of other
> > attributes in the request or other fields in paging structure entries
> > used to translate the request. The latest VT-d specification states that
> > this field is treated as Reserved(0) for implementations not supporting
> > Snoop Control (SC=0 in the Extended Capability Register). Hence add a
> > check in the code.
> >
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/intel/pasid.c | 2 +-
> >   drivers/iommu/intel/svm.c   | 1 +
> >   2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> > index f8d215d85695..9ca3c67a2058 100644
> > --- a/drivers/iommu/intel/pasid.c
> > +++ b/drivers/iommu/intel/pasid.c
> > @@ -625,7 +625,7 @@ int intel_pasid_setup_first_level(struct intel_iommu
> > *iommu,
> >   		}
> >   	}
> >
> > -	if (flags & PASID_FLAG_PAGE_SNOOP)
> > +	if ((flags & PASID_FLAG_PAGE_SNOOP) && ecap_sc_support(iommu-
> > > ecap))
> >   		pasid_set_pgsnp(pte);
> If the caller wants snoop for some reason is it correct to simply
> ignore the request when lacking of hw support? Suppose certain
> errno should be returned here...

Good catch. Perhaps I should make the cap check in a separated patch.

Best regards,
baolu