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Message-ID: <a5dc4068-050e-b651-2e8a-8e90164694a6@redhat.com>
Date: Thu, 22 Apr 2021 12:34:34 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: X86: Fix always skip to boost kernel lock holder
candidate for SEV-ES guests
On 22/04/21 10:34, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
>
> 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 <wanpengli@...cent.com>
> ---
> 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
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