linux-kernel - Re: [PATCH Part1 RFC v2 02/20] x86/sev: Save the negotiated GHCB version

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Date:   Wed, 12 May 2021 16:31:03 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        tglx@...utronix.de, jroedel@...e.de, thomas.lendacky@....com,
        pbonzini@...hat.com, mingo@...hat.com, dave.hansen@...el.com,
        rientjes@...gle.com, seanjc@...gle.com, peterz@...radead.org,
        hpa@...or.com, tony.luck@...el.com
Subject: Re: [PATCH Part1 RFC v2 02/20] x86/sev: Save the negotiated GHCB
 version

On Wed, May 12, 2021 at 09:03:41AM -0500, Brijesh Singh wrote:
> Version 2 of the spec adds bunch of NAEs, and several of them are
> optional except the hyervisor features NAE. IMO, a guest should bump the
> GHCB version only after it has implemented all the required NAEs from
> the version 2. It may help during the git bisect of the guest kernel --
> mainly when the hypervisor supports the higher version.

Aha, so AFAICT, the version bump should happen in patch 3 which adds
that HV features NAE - not in a separate one after that. The logic
being, with the patch which adds the functionality needed, you mark the
guest as supporting v2.

-- 
Regards/Gruss,
    Boris.

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