From: Yuki Shibuya <shibuya.yk@xxxxxxxxxxxxxx> This patch has been added to the 3.18 stable tree. If you have any objections, please let us know. =============== [ Upstream commit 321c5658c5e9192dea0d58ab67cf1791e45b2b26 ] Non maskable interrupts (NMI) are preferred to interrupts in current implementation. If a NMI is pending and NMI is blocked by the result of nmi_allowed(), pending interrupt is not injected and enable_irq_window() is not executed, even if interrupts injection is allowed. In old kernel (e.g. 2.6.32), schedule() is often called in NMI context. In this case, interrupts are needed to execute iret that intends end of NMI. The flag of blocking new NMI is not cleared until the guest execute the iret, and interrupts are blocked by pending NMI. Due to this, iret can't be invoked in the guest, and the guest is starved until block is cleared by some events (e.g. canceling injection). This patch injects pending interrupts, when it's allowed, even if NMI is blocked. And, If an interrupts is pending after executing inject_pending_event(), enable_irq_window() is executed regardless of NMI pending counter. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Yuki Shibuya <shibuya.yk@xxxxxxxxxxxxxx> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d77189c..390420b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6056,12 +6056,10 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win) } /* try to inject new event if pending */ - if (vcpu->arch.nmi_pending) { - if (kvm_x86_ops->nmi_allowed(vcpu)) { - --vcpu->arch.nmi_pending; - vcpu->arch.nmi_injected = true; - kvm_x86_ops->set_nmi(vcpu); - } + if (vcpu->arch.nmi_pending && kvm_x86_ops->nmi_allowed(vcpu)) { + --vcpu->arch.nmi_pending; + vcpu->arch.nmi_injected = true; + kvm_x86_ops->set_nmi(vcpu); } else if (kvm_cpu_has_injectable_intr(vcpu)) { /* * Because interrupts can be injected asynchronously, we are @@ -6231,10 +6229,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) if (inject_pending_event(vcpu, req_int_win) != 0) req_immediate_exit = true; /* enable NMI/IRQ window open exits if needed */ - else if (vcpu->arch.nmi_pending) - kvm_x86_ops->enable_nmi_window(vcpu); - else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win) - kvm_x86_ops->enable_irq_window(vcpu); + else { + if (vcpu->arch.nmi_pending) + kvm_x86_ops->enable_nmi_window(vcpu); + if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win) + kvm_x86_ops->enable_irq_window(vcpu); + } if (kvm_lapic_enabled(vcpu)) { /* -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html