Re: [PATCH v10 09/41] KVM: guest_memfd: Filter both shared and private when invalidating

[Sean Christopherson]

On Tue, Aug 25, 2026, Michael Roth wrote:
> On Wed, Aug 26, 2026 at 12:13:47AM +0800, Xiaoyao Li wrote:
> > On 8/20/2026 9:32 AM, Sean Christopherson wrote:
> > > And vice versa, a PUNCH_HOLE on a SHARED gmem (if userspace is
> > > using an INIT_SHARED gmem for the shared branch of a memslot) could invalidate the
> > > PRIVATE mappings (of a different gmem instance).
> > 
> > I'm wondering now how this could happen.
> > 
> > the requirement for PUNCH_HOLE on gmem to trigger mapping invalidation is
> > the gmem is bound with the memslot. But how can a memslot bound with two
> > gmem instances?
> 
> I think this is for when userspace uses an mmap'able guest_memfd instance
> to handle shared memory, and a 'normal' guest_memfd instance for private
> memory. Each instance is bound to the same memslot/GPA range, and
> KVM_SET_MEMORY_ATTRIBUTES handles switching between the 2.

Yep, exactly.