linux-kernel - Re: [PATCH 04/10] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state

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Message-ID: <6617e1f2-23dd-9132-d866-7780663533c3@redhat.com>
Date:   Wed, 23 Jun 2021 23:53:47 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH 04/10] KVM: SVM: add warning for mistmatch between AVIC
 state and AVIC access page state

On 23/06/21 13:29, Maxim Levitsky wrote:
> It is never a good idea to enter a guest when the AVIC state doesn't match
> the state of the AVIC MMIO memory slot.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>   arch/x86/kvm/svm/svm.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 12c06ea28f5c..50405c561394 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3780,6 +3780,9 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
>   
>   	pre_svm_run(vcpu);
>   
> +	WARN_ON_ONCE(vcpu->kvm->arch.apic_access_memslot_enabled !=
> +		     kvm_vcpu_apicv_active(vcpu));
> +
>   	sync_lapic_to_cr8(vcpu);
>   
>   	if (unlikely(svm->asid != svm->vmcb->control.asid)) {
> 

For patches 4-6, can the warnings actually fire without the fix in patch 2?

Paolo