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

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> -----Original Message-----
> From: Jason Gunthorpe <[email protected]>
> Sent: Wednesday, August 5, 2026 1:53 PM
> To: Deucher, Alexander <[email protected]>
> Cc: Hegde, Vasant <[email protected]>; Limonciello, Mario
> <[email protected]>; Kuehling, Felix <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; Suthikulpanit, Suravee
> <[email protected]>; [email protected]; Longia,
> Amandeep Kaur <[email protected]>
> Subject: Re: [PATCH 2/2] iommu/amd: Force identity mode for selected GPUs
> only
>
> On Wed, Aug 05, 2026 at 05:22:22PM +0000, Deucher, Alexander wrote:
>
> > IIRC, they supported SME, but it wasn't usable due to other
> > limitations (e.g., the requirement for identity mappings due to the
> > display hw bug and the latency impact of encryption for displays in
> > system memory).  Do you could effectively pick either SME or displays.
>
> IMHO the GPU driver should fail if it cannot work because it can't reach the
> IOVA space requried for SME ...
>
> I don't think this should be a iommu problem to deal with

That means no display for the user which is a not a good user experience. Most users of systems with integrated graphics would probably prefer displays over SME.

Alex