From 3252026aa92e2f271a4d5292d233356fbdbdd8a6 Mon Sep 17 00:00:00 2001 From: Yuki Shibuya Date: Thu, 24 Mar 2016 05:17:03 +0000 Subject: [PATCH] KVM: x86: Inject pending interrupt even if pending nmi exist commit 321c5658c5e9192dea0d58ab67cf1791e45b2b26 upstream. 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. Signed-off-by: Yuki Shibuya Suggested-by: Paolo Bonzini Signed-off-by: Paolo Bonzini [bwh: Backported to 3.2: - vcpu_enter_guest() is simpler because inject_pending_event() can't fail - Adjust context] Signed-off-by: Ben Hutchings --- arch/x86/kvm/x86.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 09dab5bc4995..da1a1261aac1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5634,12 +5634,10 @@ static void inject_pending_event(struct kvm_vcpu *vcpu) } /* 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_interrupt(vcpu)) { if (kvm_x86_ops->interrupt_allowed(vcpu)) { kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu), @@ -5742,7 +5740,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) /* enable NMI/IRQ window open exits if needed */ if (vcpu->arch.nmi_pending) kvm_x86_ops->enable_nmi_window(vcpu); - else if (kvm_cpu_has_interrupt(vcpu) || req_int_win) + if (kvm_cpu_has_interrupt(vcpu) || req_int_win) kvm_x86_ops->enable_irq_window(vcpu); if (kvm_lapic_enabled(vcpu)) { -- 2.39.2