Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a struct kvm_gmem_private

Peter Xu
2024-10-16T23:49:39Z

On Wed, Oct 16, 2024 at 07:51:57PM -0300, Jason Gunthorpe wrote:
> On Wed, Oct 16, 2024 at 04:16:17PM -0400, Peter Xu wrote:
> >
> > Is there chance that when !CoCo will be supported, then external modules
> > (e.g. VFIO) can reuse the old user mappings, just like before gmemfd?
> >
> > To support CoCo, I understand gmem+offset is required all over the places.
> > However in a non-CoCo context, I wonder whether the other modules are
> > required to stick with gmem+offset, or they can reuse the old VA ways,
> > because how it works can fundamentally be the same as before, except that
> > the folios now will be managed by gmemfd.
>
> My intention with iommufd was to see fd + offest as the "new" way
> to refer to all guest memory and discourage people from using VMA
> handles.

Does it mean anonymous memory guests will not be supported at all for
iommufd?

Indeed it's very rare now, lose quite some flexibility (v.s. fd based), and
I can't think of a lot besides some default configs or KSM users (which I
would expect rare), but still I wonder there're other use cases that people
would still need to stick with anon, hence fd isn't around.

Thanks,

--
Peter Xu