Re: [edk2-devel] [PATCH v9 0/4] Add safe unaccepted memory behavior

["Ard Biesheuvel" <ardb@kernel.org>]

On Tue, 24 Jan 2023 at 23:42, Lendacky, Thomas via groups.io
<thomas.lendacky=amd.com@groups.io> wrote:
>
> On 1/16/23 04:28, Gerd Hoffmann via groups.io wrote:
> > On Fri, Jan 13, 2023 at 10:34:15AM -0800, Dave Hansen wrote:
> >> On 1/13/23 10:23, Dionna Glaze via groups.io wrote:
> >>>> However, *NONE* of this points me in the direction of saying that we
> >>>> should have an OS/firmware protocol to negotiate whether the firmware or
> >>>> OS does page acceptance other than the existing UEFI memory map bit.
> >>> We know of distributions that are going to release SEV-SNP support
> >>> without unaccepted memory support,
> >>
> >> Well, I guess that's a bit of a different problem.
> >>
> >> I'd love to hear from the distros what they're planning on carrying
> >> outside of mainline and what their plans are for the kernel side of this
> >> series.
> >
> > Fedora has near zero additional patches, so it pretty much depends on
> > how mainline merges stuff.  If SEV-SNP or TDX or both will land in an
> > upstream release before support for unaccepted memory lands too you'll
>
> Sorry, just saw this...
>
> SEV-SNP guest support has already landed upstream and is part of the 5.19
> kernel. So without this interface, anyone using a newer OVMF with a 5.19
> to whatever kernel just before unaccepted memory finally gets pulled into,
> would have issues.
>

Exactly. And my Fedora kernel has those bits enabled by default.

So I suppose the way forward here is to expose this protocol only on
OVMF builds that target SEV-SNP, instead of introducing it as a
generic CoCo feature.

On the Linux side, we can make its boot time invocation dependent on
CONFIG_AMD_MEM_ENCRYPT as well as CONFIG_UNACCEPTED_MEMORY.