Re: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms

Borislav Petkov
2022-11-29T08:40:56Z

On Tue, Nov 29, 2022 at 01:15:39AM +0000, Michael Kelley (LINUX) wrote:
> So that's why I'm suggesting CC_VENDOR_AMD_VTOM.

There's no CC_VENDOR_AMD_VTOM. How many times do I need to explain this?!
CC_VENDOR is well the CC vendor - not some special case.

IOW, the goal here is for generic SNP functionality to be the same for
*all* SNP guests. We won't do the AMD's version of vTOM enablement,
Hyper-V's version of vTOM enablement and so on. It must be a single
vTOM feature which works on *all* hypervisors as vTOM is a generic SNP
feature - not Hyper-V feature.

> Of course, when you go from N=1 hypervisors (i.e., KVM) to N=2 (KVM
> and Hyper-V, you find some places where incorrect assumptions were
> made or some generalizations are needed. Dexuan Cui's patch set for
> TDX support is fixing those places that he has encountered. But with
> those fixes, the TDX support will JustWork(tm) for Linux guests on
> Hyper-V.

That sounds like the right direction to take.

> I haven't gone deeply into the situation with AMD C-bit support on
> Hyper-V. Tianyu Lan's set of patches for that support is a bit bigger,
> and I'm planning to look closely to understand whether it's also just
> fixing incorrect assumptions and such, or whether they really are
> some differences with Hyper-V. If there are differences, I want to
> understand why.

You and me too. So I guess we should look at Tianyu's set first.

Thx.

--
Regards/Gruss,
Boris.