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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id 16sm1642520ejw.0.2021.04.22.03.34.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Apr 2021 03:34:36 -0700 (PDT) Subject: Re: [PATCH] KVM: X86: Fix always skip to boost kernel lock holder candidate for SEV-ES guests To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel References: <1619080459-30032-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Thu, 22 Apr 2021 12:34:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <1619080459-30032-1-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/04/21 10:34, Wanpeng Li wrote: > From: Wanpeng Li > > Commit f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under > SEV-ES") prevents hypervisor accesses guest register state when the guest is > running under SEV-ES. The initial value of vcpu->arch.guest_state_protected > is false, it will not be updated in preemption notifiers after this commit which > means that the kernel spinlock lock holder will always be skipped to boost. Let's > fix it by always treating preempted is in the guest kernel mode, false positive > is better than skip completely. > > Fixes: f1c6366e3043 (KVM: SVM: Add required changes to support intercepts under SEV-ES) > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/x86.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index d696a9f..e52ca09 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11151,6 +11151,9 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu) > > bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) > { > + if (vcpu->arch.guest_state_protected) > + return true; > + > return vcpu->arch.preempted_in_kernel; > } > > Queued, thanks. Paolo