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Peter Anvin" , Peter Shier , kvm@vger.kernel.org Subject: [PATCH] KVM: X86: always reset st->preempted in record_steal_time() Date: Fri, 28 May 2021 01:33:58 +0800 Message-Id: <20210527173358.49427-1-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan st->preempted needs to be reset in record_steal_time() to clear the KVM_VCPU_PREEMPTED bit. But the commit 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID") made it cleared conditionally and KVM_VCPU_PREEMPTED might not be cleared when entering into the guest. Also make st->preempted be only read once, so that trace_kvm_pv_tlb_flush() and kvm_vcpu_flush_tlb_guest() is consistent with same value of st->preempted. Cc: Oliver Upton Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID") Signed-off-by: Lai Jiangshan --- arch/x86/kvm/x86.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bbc4e04e67ad..b8a7259ebd14 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3101,10 +3101,14 @@ static void record_steal_time(struct kvm_vcpu *vcpu) * expensive IPIs. */ if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) { + u8 st_preempted = xchg(&st->preempted, 0); + trace_kvm_pv_tlb_flush(vcpu->vcpu_id, - st->preempted & KVM_VCPU_FLUSH_TLB); - if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) + st_preempted & KVM_VCPU_FLUSH_TLB); + if (st_preempted & KVM_VCPU_FLUSH_TLB) kvm_vcpu_flush_tlb_guest(vcpu); + } else { + st->preempted = 0; } vcpu->arch.st.preempted = 0; -- 2.19.1.6.gb485710b