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Date:   Thu, 28 Sep 2023 09:03:31 -0700
In-Reply-To: <20230928150428.199929-4-mlevitsk@redhat.com>
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References: <20230928150428.199929-1-mlevitsk@redhat.com> <20230928150428.199929-4-mlevitsk@redhat.com>
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Subject: Re: [PATCH 3/5] x86: KVM: SVM: refresh AVIC inhibition in svm_leave_nested()
From:   Sean Christopherson <seanjc@google.com>
To:     Maxim Levitsky <mlevitsk@redhat.com>
Cc:     kvm@vger.kernel.org, Will Deacon <will@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Paolo Bonzini <pbonzini@redhat.com>, x86@kernel.org,
        Robin Murphy <robin.murphy@arm.com>, iommu@lists.linux.dev,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <joro@8bytes.org>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
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On Thu, Sep 28, 2023, Maxim Levitsky wrote:
> svm_leave_nested() similar to a nested VM exit, get the vCPU out of nested
> mode and thus should end the local inhibition of AVIC on this vCPU.
> 
> Failure to do so, can lead to hangs on guest reboot.
> 
> Raise the KVM_REQ_APICV_UPDATE request to refresh the AVIC state of the
> current vCPU in this case.
> 
> Cc: stable@vger.kernel.org

Unnecessary newline.

Fixes: f44509f849fe ("KVM: x86: SVM: allow AVIC to co-exist with a nested guest running")

> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/svm/nested.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index dd496c9e5f91f28..3fea8c47679e689 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1253,6 +1253,9 @@ void svm_leave_nested(struct kvm_vcpu *vcpu)
>  
>  		nested_svm_uninit_mmu_context(vcpu);
>  		vmcb_mark_all_dirty(svm->vmcb);
> +
> +		if (kvm_apicv_activated(vcpu->kvm))
> +			kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
>  	}
>  
>  	kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
> -- 
> 2.26.3
>