Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx> writes: > This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381 I can also reproduce this easily with Linux as L1 by "slowing it down" eg. running with ept = 0 I suggest changing the subject to - KVM: nVMX: Fix race that incorrectly injects L1's irq to L2 > If we didn't inject a still-pending event to L1 since nested_run_pending, > KVM_REQ_EVENT should be requested after the vmexit in order to inject the > event to L1. However, current log blindly request a KVM_REQ_EVENT even if What's current "log" ? Do you mean current "code" ? > there is no still-pending event to L1 which blocked by nested_run_pending. > There is a race which lead to an interrupt will be injected to L2 which > belong to L1 if L0 send an interrupt to L1 during this window. > > VCPU0 another thread > > L1 intr not blocked on L2 first entry > vmx_vcpu_run req event > kvm check request req event > check_nested_events don't have any intr > not nested exit > intr occur (8254, lapic timer etc) > inject_pending_event now have intr > inject interrupt > > This patch fix this race by introduced a l1_events_blocked field in nested_vmx > which indicates there is still-pending event which blocked by nested_run_pending, > and smart request a KVM_REQ_EVENT if there is a still-pending event which blocked > by nested_run_pending. > > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx> > --- > arch/x86/kvm/vmx.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f4e5aed..fe69c49 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -372,6 +372,7 @@ struct nested_vmx { > u64 vmcs01_tsc_offset; > /* L2 must run next, and mustn't decide to exit to L1. */ > bool nested_run_pending; > + bool l1_events_blocked; > /* > * Guest pages referred to in vmcs02 with host-physical pointers, so > * we must keep them pinned while L2 runs. > @@ -7380,8 +7381,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) > * we did not inject a still-pending event to L1 now because of > * nested_run_pending, we need to re-enable this bit. > */ > - if (vmx->nested.nested_run_pending) > + if (to_vmx(vcpu)->nested.l1_events_blocked) { Is to_vmx() necessary since we alredy have the vmx pointer ? > + to_vmx(vcpu)->nested.l1_events_blocked = false; > kvm_make_request(KVM_REQ_EVENT, vcpu); > + } > > vmx->nested.nested_run_pending = 0; > > @@ -8197,15 +8200,20 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr) > > if (nested_cpu_has_preemption_timer(get_vmcs12(vcpu)) && > vmx->nested.preemption_timer_expired) { > - if (vmx->nested.nested_run_pending) > + if (vmx->nested.nested_run_pending) { > + vmx->nested.l1_events_blocked = true; > return -EBUSY; > + } > nested_vmx_vmexit(vcpu, EXIT_REASON_PREEMPTION_TIMER, 0, 0); > return 0; > } > > if (vcpu->arch.nmi_pending && nested_exit_on_nmi(vcpu)) { > - if (vmx->nested.nested_run_pending || > - vcpu->arch.interrupt.pending) > + if (vmx->nested.nested_run_pending) { > + vmx->nested.l1_events_blocked = true; > + return -EBUSY; > + } > + if (vcpu->arch.interrupt.pending) > return -EBUSY; > nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI, > NMI_VECTOR | INTR_TYPE_NMI_INTR | > @@ -8221,8 +8229,10 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr) > > if ((kvm_cpu_has_interrupt(vcpu) || external_intr) && > nested_exit_on_intr(vcpu)) { > - if (vmx->nested.nested_run_pending) > + if (vmx->nested.nested_run_pending) { > + vmx->nested.l1_events_blocked = true; > return -EBUSY; > + } > nested_vmx_vmexit(vcpu, EXIT_REASON_EXTERNAL_INTERRUPT, 0, 0); > } Also, I am wondering isn't it enough to just do this to avoid this race ? static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu) { - return (!to_vmx(vcpu)->nested.nested_run_pending && + return (!is_guest_mode(vcpu) && + !to_vmx(vcpu)->nested.nested_run_pending && vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) && !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & Thanks, Bandan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
