Re: [PATCH 2/2] iommu/amd: Force identity mode for selected GPUs only

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Jul 30, 2026 at 04:56:37PM +0530, Vasant Hegde wrote:

> Based on discussion so far in this thread and the link Mario shared earlier [1]:
>   - We still need identity mapping for APUs. I will fine tune the patch based on
> the discussion in this thread.

IMHO if certain HW has broken support for PAGING (eg because it can't
handle the isochronous needs) then it should be quirked and blocked
properly.

I thought the issue here was the PASID check forcing identity and
accidently capturing these raven chips too? It should just be moved
out to a normal quirk..

>   - Its fine to drop SNP check
>   - I am still not sure its safe to drop SME check (CC_ATTR_MEM_ENCRYPT)
>     Because here were are putting all APUs in identity mode.
>     Commit ea68573d408f explicitly error out for RAVEN and some of the older APU
> platform didn't support SME. But not sure about newer ones.

That's quite a hacky check to make in that commit..

> So I am inclined to keep SME check for now. Once this patch stabilized we can
> revisit the SME check?

The SME check makes no sense either, but if you want to stage things
I'm OK with it.

Jason