Re: [PATCH v10 09/16] KVM: guest_memfd: Track shared memory support in memslot

[Fuad Tabba <tabba@google.com>]

On Wed, 4 Jun 2025 at 13:25, David Hildenbrand <david@redhat.com> wrote:
>
> On 27.05.25 20:02, Fuad Tabba wrote:
> > Track whether a guest_memfd-backed memslot supports shared memory within
> > the memslot itself, using the flags field. The top half of memslot flags
> > is reserved for internal use in KVM. Add a flag there to track shared
> > memory support.
> >
> > This saves the caller from having to check the guest_memfd-backed file
> > for this support, a potentially more expensive operation due to the need
> > to get/put the file.
> >
> > Suggested-by: David Hildenbrand <david@redhat.com>
> > Signed-off-by: Fuad Tabba <tabba@google.com>
> > ---
> >   include/linux/kvm_host.h | 11 ++++++++++-
> >   virt/kvm/guest_memfd.c   |  8 ++++++--
> >   2 files changed, 16 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index ba83547e62b0..edb3795a64b9 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -54,7 +54,8 @@
> >    * used in kvm, other bits are visible for userspace which are defined in
> >    * include/uapi/linux/kvm.h.
> >    */
> > -#define KVM_MEMSLOT_INVALID  (1UL << 16)
> > +#define KVM_MEMSLOT_INVALID          (1UL << 16)
> > +#define KVM_MEMSLOT_SUPPORTS_SHARED  (1UL << 17)
>
> Should there be a "GMEM" in there?

I'll change it to KVM_MEMSLOT_SUPPORTS_GMEM_SHARED. I thought of
adding _MEM as well, but it starts getting too long :)

Thanks,
/fuad


> --
> Cheers,
>
> David / dhildenb
>