linux-kernel - Re: [PATCH v3] x86/sev: Add SEV-SNP guest feature negotiation support

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Message-ID: <Y7QRkzxg1HW9wMCp@zn.tnic>
Date:   Tue, 3 Jan 2023 12:29:23 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Nikunj A. Dadhania" <nikunj@....com>
Cc:     David Rientjes <rientjes@...gle.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, kvm@...r.kernel.org, mingo@...hat.com,
        tglx@...utronix.de, dave.hansen@...ux.intel.com, seanjc@...gle.com,
        pbonzini@...hat.com, thomas.lendacky@....com, michael.roth@....com,
        stable@...nel.org
Subject: Re: [PATCH v3] x86/sev: Add SEV-SNP guest feature negotiation support

On Tue, Jan 03, 2023 at 09:07:14AM +0530, Nikunj A. Dadhania wrote:
> Currently, GHCBData[24:63] is unused. If we intend to use the bit range(40bits), GHCB spec 
> will need to be updated. And probably would not be enough.

My fear too...

> As the termination request is done using GHCB MSR protocol, exit codes cannot be used.

We need to figure out some other way of communicating to the guest owner because
of which feature the guest refused booting.

-- 
Regards/Gruss,
    Boris.

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