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Date:   Tue, 29 Nov 2022 09:40:46 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     "Michael Kelley (LINUX)" <mikelley@microsoft.com>
Cc:     "hpa@zytor.com" <hpa@zytor.com>, KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
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Subject: Re: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use
 standard coco mechanisms
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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.

https://people.kernel.org/tglx/notes-about-netiquette