Re: [PATCH RFCv1 08/14] iommufd: Add IOMMU_VIOMMU_SET_DEV_ID ioctl

Jason Gunthorpe
2024-06-06T18:24:31Z

On Sun, Jun 02, 2024 at 08:25:34PM -0700, Nicolin Chen wrote:

> > I understand the appeal of doing this has been to minimize qemu
> > changes in its ACPI parts if we tackle that instead maybe we should
> > just not implement viommu to multiple piommu. It is somewhat
> > complicated.
>
> Would you please clarify that suggestion "not implement viommu
> to multiple piommu"?
>
> For regular nesting (SMMU), we are still doing one vSMMU in the
> VMM, though VCMDQ case would be an exception....

This is what I mean, always do multiple vSMMU if there are multiple
physical pSMMUs. Don't replicate any virtual commands across pSMMUs.

Jason