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

Jason Gunthorpe
2024-10-16T23:54:30Z

On Wed, Oct 16, 2024 at 07:49:31PM -0400, Peter Xu wrote:
> 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?

No, they can use the "old" way with normal VMA's still, or they can
use an anonymous memfd with the new way..

I just don't expect to have new complex stuff built on the VMA
interface - I don't expect guestmemfd VMAs to work.

Jason