linux-kernel - Re: [PATCH] KVM: x86: Allow XSAVES on CPUs where host doesn't use it due to an errata

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Message-ID: <CALMp9eQvLpYdq=2cYyOBERBh2G+xubo6Mb0crWO=dugpie4BRg@mail.gmail.com>
Date:   Thu, 30 Nov 2023 15:57:38 -0800
From:   Jim Mattson <jmattson@...gle.com>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Maxim Levitsky <mlevitsk@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Allow XSAVES on CPUs where host doesn't use it
 due to an errata

On Thu, Nov 30, 2023 at 2:00 PM Maciej S. Szmigiero
<mail@...iej.szmigiero.name> wrote:
> I think that if particular guest would work on bare metal it should
> work on "-cpu host" too - no tinkering should be required for such
> basic functionality as being able to successfully finish booting.

I disagree. Let's not focus on one particular erratum. If, for
whatever reason, the host kernel is booted with "noxsaves," I don't
think KVM should allow a guest to bypass that directive.