linux-kernel - Re: [PATCH v8 4/4] kvm: vmx: virtualize split lock detection

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Message-ID: <87y2qwmszt.fsf@nanos.tec.linutronix.de>
Date:   Wed, 15 Apr 2020 21:47:02 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v8 4/4] kvm: vmx: virtualize split lock detection

Xiaoyao Li <xiaoyao.li@...el.com> writes:

> Due to the fact that TEST_CTRL MSR is per-core scope, i.e., the sibling
> threads in the same physical CPU core share the same MSR, only
> advertising feature split lock detection to guest when SMT is disabled
> or unsupported, for simplicitly.

That's not for simplicity. It's for correctness because you cannot
provide consistent state to a guest.

Thanks,

        tglx