Re: [PATCH v2 6/8] iommu/amd: Enhance domain_alloc_user() to allocate PASID capable domain

[Jason Gunthorpe <jgg@ziepe.ca>]

On Wed, Oct 16, 2024 at 02:48:04AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@ziepe.ca>
> > Sent: Tuesday, October 15, 2024 8:40 PM
> > 
> > On Tue, Oct 15, 2024 at 08:41:48AM +0000, Tian, Kevin wrote:
> > 
> > > > -	return do_iommu_domain_alloc(type, dev, flags, AMD_IOMMU_V1);
> > > > +	/* Allocate v2 page table if IOMMU and device supports PASID. */
> > > > +	if (flags & IOMMU_HWPT_ALLOC_PASID) {
> > > > +		if (!amd_iommu_pasid_supported() ||
> > > > +		    !pdev_pasid_supported(dev_data))
> > > > +			return ERR_PTR(-EINVAL);
> > >
> > > Just check the iommu capability here? IMHO it's a sane case to first
> > > create a PASID-compatible domain for a device which doesn't support
> > > PASID and then attach the domain to a PASID-capable device later.
> > 
> > The point of this series is to allow AMD to select the v1 format as
> > often as possible because v1 has better performance than v2
>
> If the user wants better performance then it should not set the flag.

Well, I do tend to agree with that, you mean remove the
pdev_pasid_supported() ?

Jason