linux-kernel - Re: [PATCH 02/22] x86/srso: Set CPUID feature bits independently of bug or mitigation status

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Message-ID: <20230821140619.GBZONvWz+iwQZwx/sC@fat_crate.local>
Date:   Mon, 21 Aug 2023 16:06:19 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andrew Cooper <andrew.cooper3@...rix.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Babu Moger <babu.moger@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, David.Kaplan@....com,
        Nikolay Borisov <nik.borisov@...e.com>,
        gregkh@...uxfoundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 02/22] x86/srso: Set CPUID feature bits independently of
 bug or mitigation status

On Mon, Aug 21, 2023 at 10:27:50AM +0100, Andrew Cooper wrote:
> This patch is necessary but not sufficient to fix the bugs.  There needs
> to be a !cpu_has_hypervisor in here.

Yes, but in a separate patch.

And I still don't know what exactly we're going to support when Linux
runs as a guest. For example, live migration between Zen1/2 and Zen3/4
won't work due to the alternatives patching, for example...

IBPB won't work either because we detect those feature bits only once
during boot, like every other feature bit...

Whatever it is, I'd like to see it written down first so that we go and
look it up and point to it when someone's changing that code.

Thx.

-- 
Regards/Gruss,
    Boris.

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