Re: [RFC PATCH v2 9/9] iommu/riscv: Add riscv_iommu_attach_dev_nested

[Gong Shuai]

Hi Jason,

On 11/10/2026 9:16 PM, Jason Gunthorpe wrote:
> On Tue, Nov 10, 2026 at 07:51:37PM +0800, Gong Shuai wrote:
>
> >   2. Use the guest PSCID directly, but allocate a separate host GSCID for
> >      each vIOMMU.
>
> This is the right model. The viommu should allocate the GSCID directly
> and keep it for the lifetime of the VM.

Thanks for the confirmation. The new version will use this scheme.

> >   3. Share the GSCID and maintain a per-vIOMMU mapping from each guest
> >      PSCID to a host-allocated PSCID.
>
> AMD is doing this because they don't have something like a GSCID.

Understood. This approach makes sense.

Thanks,
Shuai

> Jason