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AJvYcCX4bmr86map0Z9Qyuq1ByQFMHsAj6hUj2Gv0Tt8wp2U4FY8knQ2kj9e0aEpDzCXYZ4v0oE=@vger.kernel.org X-Gm-Message-State: AOJu0Yz91mbMo0juvmjv+H2FyxwH5KjyUputeoHawMcQvCUZwyHdEjIz Z4HnRZn04txvQXesbQFYVzI3ZvlDn3wjX3imx7OOgdlFgrz92nhwbSVVvJ6AF4H9B0QmXlLg0vD soX1Weg== X-Received: from pgg23.prod.google.com ([2002:a05:6a02:4d97:b0:c6d:c1c4:8cf5]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:cf8d:b0:38e:9c64:bd39 with SMTP id adf61e73a8af0-394672ce209mr14662564637.44.1771342869976; Tue, 17 Feb 2026 07:41:09 -0800 (PST) Date: Tue, 17 Feb 2026 07:41:08 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260215140402.24659-1-76824143@qq.com> Message-ID: Subject: Re: [PATCH 2/3] KVM: x86: Skip IN_GUEST_MODE vCPUs in kvm_vcpu_on_spin main loop From: Sean Christopherson To: 76824143@qq.com Cc: pbonzini@redhat.com, kvm@vger.kernel.org, zhanghao Content-Type: text/plain; charset="us-ascii" On Sun, Feb 15, 2026, 76824143@qq.com wrote: > From: zhanghao > > Add a check in the kvm_vcpu_on_spin() main loop to skip vCPUs > that are already running in guest mode. > > Reduces unnecessary yield_to() calls and VM exits. > > Signed-off-by: zhanghao > --- > virt/kvm/kvm_main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 476ecdb18bdd..663df3a121c8 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -4026,6 +4026,10 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) > vcpu = xa_load(&kvm->vcpu_array, idx); > if (!READ_ONCE(vcpu->ready)) > continue; > + > + if (READ_ONCE(vcpu->mode) == IN_GUEST_MODE) > + continue; This should generally not happen, as vcpu->ready should only be true when a vCPU is scheduled out. Although it does look like there's a race in kvm_vcpu_wake_up() where vcpu->ready could be left %true, e.g. if the task was delyed or preempted after __kvm_vcpu_wake_up(), before the "WRITE_ONCE(vcpu->ready, true)". Not sure how best to handle that scenario. > + > if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu)) > continue; > > -- > 2.39.2 >