Re: [PATCH v2 03/13] KVM: guest_memfd: Invalidate SHARED GPAs if gmem supports INIT_SHARED

David Hildenbrand
2025-10-10T14:10:03Z

On 04.10.25 01:25, Sean Christopherson wrote:
> When invalidating gmem ranges, e.g. in response to PUNCH_HOLE, process all
> possible range types (PRIVATE vs. SHARED) for the gmem instance. Since
> since guest_memfd doesn't yet support in-place conversions, simply pivot
> on INIT_SHARED as a gmem instance can currently only have private or shared
> memory, not both.
>
> Failure to mark shared GPAs for invalidation is benign in the current code
> base, as only x86's TDX consumes KVM_FILTER_{PRIVATE,SHARED}, and TDX
> doesn't yet support INIT_SHARED with guest_memfd. However, invalidating
> only private GPAs is conceptually wrong and a lurking bug, e.g. could
> result in missed invalidations if ARM starts filtering invalidations based
> on attributes.
>
> Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Cheers

David / dhildenb