linux-kernel - Re: [PATCH 05/15] KVM: VMX: Disable preemption when probing user return MSRs

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Message-ID: <CALMp9eQOZyf=U=Y-4CLpB9=nBfVPjOQzcURrTAUNZyugiischw@mail.gmail.com>
Date:   Tue, 4 May 2021 16:36:46 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Reiji Watanabe <reijiw@...gle.com>
Subject: Re: [PATCH 05/15] KVM: VMX: Disable preemption when probing user
 return MSRs

On Tue, May 4, 2021 at 10:17 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
> the MSR holds a different value per logical CPU, the WRMSR could corrupt
> the host's value if KVM is preempted between the RDMSR and WRMSR, and
> then rescheduled on a different CPU.
>
> Opportunistically land the helper in common x86, SVM will use the helper
> in a future commit.
>
> Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
> Cc: stable@...r.kernel.org
> Cc: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>