Commit 321c5658 authored Mar 24, 2016 by Yuki Shibuya Committed by Paolo Bonzini Apr 01, 2016

KVM: x86: Inject pending interrupt even if pending nmi exist



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@vger.kernel.org
Signed-off-by: Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent c26e5f30

arch/x86/kvm/x86.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -6095,12 +6095,10 @@ 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)) {
		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
		@@ -6569,10 +6567,12 @@ 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)
		else {
		if (vcpu->arch.nmi_pending)
		kvm_x86_ops->enable_nmi_window(vcpu);
		else if (kvm_cpu_has_injectable_intr(vcpu) \|\| req_int_win)
		if (kvm_cpu_has_injectable_intr(vcpu) \|\| req_int_win)
		kvm_x86_ops->enable_irq_window(vcpu);
		}

		if (kvm_lapic_enabled(vcpu)) {
		update_cr8_intercept(vcpu);

Admin message