Re: [PATCH v2 21/26] iommu/amd: Map kvmfd to shared translate device ID for vIOMMU

[Suthikulpanit, Suravee]

Jason,

On 6/1/2026 8:35 PM, Jason Gunthorpe wrote:
> On Thu, May 28, 2026 at 05:17:33AM +0000, Suravee Suthikulpanit wrote:
> > Add per-PCI-segment kvmfd xarray amd_iommu_kvmfd_trans_entry with
> > refcounted so all vIOMMUs for one VM share one translate-device-id and
> > GPA->SPA DTE.
>
> What? There should no KVM in the viommu implementation.
>
> I can't understand why you did this.
>
> AFAICT the HW needs some unused devid "TransDevID" for some
> purpose. This is pretty sketchy, but OK..
>
> The ID should be affiliated with every nest parent domain, or maybe
> every vIOMMU.
>
> It has nothing to do with KVM. You can't assume anything about iommufd
> is constructing the viommu based on the KVM.
>
> The only acceptable use of KVM in iommufd land is to get some CPU
> specific shared information which this is not doing.
>
> So no to any KVM stuff in this series.

I will remove kvmfd stuff from this series, and decouple it from 
TransDevID management.

However, in upcoming series, when introduces vIOMMU EventLog and PPRLog 
virtualization support, we need kvm to get SVM AVIC information in order 
to setup extended interrupt remapping for EventLog and PPRLog 
interrupts. Any suggestions on how to achieve this if you do not want to 
pass kvmfd from userspace?

Thanks,
Suravee