From 2ce7107febf15d8954762c8e7036912eeb184209 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Tue, 18 May 2021 05:00:33 -0700 Subject: [PATCH] KVM: X86: Fix vCPU preempted state from guest's point of view commit 1eff0ada88b48e4ac1e3fe26483b3684fedecd27 upstream. Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) avoids to access pv tlb shootdown host side logic when this pv feature is not exposed to guest, however, kvm_steal_time.preempted not only leveraged by pv tlb shootdown logic but also mitigate the lock holder preemption issue. From guest's point of view, vCPU is always preempted since we lose the reset of kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not exposed. This patch fixes it by clearing kvm_steal_time.preempted before vmentry. Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) Reviewed-by: Sean Christopherson Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li Message-Id: <1621339235-11131-3-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 86678f8b35020..500fa170e8c5e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3015,6 +3015,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu) st->preempted & KVM_VCPU_FLUSH_TLB); if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) kvm_vcpu_flush_tlb_guest(vcpu); + } else { + st->preempted = 0; } vcpu->arch.st.preempted = 0;