Re: [PATCH RFCv2] iommu: Add domain type and flag to domain_alloc_paging()

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, Aug 09, 2024 at 12:13:47PM +0530, Vasant Hegde wrote:
> Jason,
> 
> 
> On 8/8/2024 6:38 PM, Jason Gunthorpe wrote:
> > On Wed, Aug 07, 2024 at 10:16:29PM -0300, Jason Gunthorpe wrote:
> >> On Wed, Aug 07, 2024 at 03:29:47PM -0300, Jason Gunthorpe wrote:
> >>>> @Baolu, Do we need to make any changes to intel driver?
> >>>
> >>> I think Intel ignores this issue, they have nice HW and their RID can
> >>> use both of their supported domain formats in all cases.
> >>
> >> On second thought it does need to accept, but ignore the new flags..
> > 
> > And probably HW that does not support PASID should reject the
> > IOMMU_HWPT_ALLOC_PASID flag at least.
> 
> 
> You mean error out if IOMMU or device doesnot support PASID?

Just the iommu, yes.

Like in AMD terms if there is no AMDv2 page table support then fail
it.

> > Maybe IOMMU_HWPT_ALLOC_DEV_PASID can be reasonably ignored if the HW
> > doesn't support PASID.
>  
> You mean make it as optional flag? Meaning if HW doesn't support PASID then
> still allocate a domain without PASID capability?

Yes, for the RID domain it seems harmless to ignore, I'm not really
sure on this though.

Otherwise we'd want to report pasid support through a INFO return so
userspace knows if it should specify this flag.

Jason