linux-kernel - Re: [PATCH v2] KVM: x86: Ignore MSR_AMD64_TW

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Message-ID: <169773243871.2018423.1481448432661434673.b4-ty@google.com>
Date:   Fri, 20 Oct 2023 15:56:25 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86: Ignore MSR_AMD64_TW_CFG access

On Thu, 19 Oct 2023 18:06:57 +0200, Maciej S. Szmigiero wrote:
> Hyper-V enabled Windows Server 2022 KVM VM cannot be started on Zen1 Ryzen
> since it crashes at boot with SYSTEM_THREAD_EXCEPTION_NOT_HANDLED +
> STATUS_PRIVILEGED_INSTRUCTION (in other words, because of an unexpected #GP
> in the guest kernel).
> 
> This is because Windows tries to set bit 8 in MSR_AMD64_TW_CFG and can't
> handle receiving a #GP when doing so.
> 
> [...]

Applied to kvm-x86 misc, thanks!  I added a paragraph at the end of the
changelog to capture the gist of the discussion on why we agreed that having
KVM eat MSR accesses is the least awful option.  I also tagged this for stable.

Paolo, holler if you want to grab this for v6.6 and I'll drop my copy.

[1/1] KVM: x86: Ignore MSR_AMD64_TW_CFG access
      https://github.com/kvm-x86/linux/commit/2770d4722036

--
https://github.com/kvm-x86/linux/tree/next