Re: [PATCH v3 03/70] RAMBlock/guest_memfd: Enable KVM_GUEST_MEMFD_ALLOW_HUGEPAGE

Sean Christopherson
2023-11-30T16:01:25Z

On Thu, Nov 30, 2023, David Hildenbrand wrote:
> On 30.11.23 08:32, Xiaoyao Li wrote:
> > On 11/20/2023 5:26 PM, David Hildenbrand wrote:
> > >
> > > > > ... did you shamelessly copy that from hw/virtio/virtio-mem.c ? ;)
> > > >
> > > > Get caught.
> > > >
> > > > > This should be factored out into a common helper.
> > > >
> > > > Sure, will do it in next version.
> > >
> > > Factor it out in a separate patch. Then, this patch is get small that
> > > you can just squash it into #2.
> > >
> > > And my comment regarding "flags = 0" to patch #2 does no longer apply :)
> > >
> >
> > I see.
> >
> > But it depends on if KVM_GUEST_MEMFD_ALLOW_HUGEPAGE will appear together
> > with initial guest memfd in linux (hopefully 6.8)
> > https://lore.kernel.org/all/CABgObfa=DH7FySBviF63OS9sVog_wt-AqYgtUAGKqnY5Bizivw@mail.gmail.com/
> >
>
> Doesn't seem to be in -next if I am looking at the right tree:
>
> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=next

Yeah, we punted on adding hugepage support for the initial guest_memfd merge so
as not to rush in kludgy uABI. The internal KVM code isn't problematic, we just
haven't figured out exactly what the ABI should look like, e.g. should hugepages
be dependent on THP being enabled, and if not, how does userspace discover the
supported hugepage sizes?