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[Qemu-devel] [PATCH v2] KVM: x86: Fix nmi injection failure when vcpu go


From: Zhuangyanying
Subject: [Qemu-devel] [PATCH v2] KVM: x86: Fix nmi injection failure when vcpu got blocked
Date: Thu, 25 May 2017 14:56:43 +0800

From: ZhuangYanying <address@hidden>

When spin_lock_irqsave() deadlock occurs inside the guest, vcpu threads,
other than the lock-holding one, would enter into S state because of
pvspinlock. Then inject NMI via libvirt API "inject-nmi", the NMI could
not be injected into vm.

The reason is:
1 It sets nmi_queued to 1 when calling ioctl KVM_NMI in qemu, and sets
cpu->kvm_vcpu_dirty to true in do_inject_external_nmi() meanwhile.
2 It sets nmi_queued to 0 in process_nmi(), before entering guest, because
cpu->kvm_vcpu_dirty is true.

It's not enough just to check nmi_queued to decide whether to stay in
vcpu_block() or not. NMI should be injected immediately at any situation.
Add checking KVM_REQ_NMI request plus with nmi_queued in
vm_vcpu_has_events().

Signed-off-by: Zhuang Yanying <address@hidden>
---
 arch/x86/kvm/x86.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 02363e3..2d15708 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8394,7 +8394,9 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu 
*vcpu)
        if (vcpu->arch.pv.pv_unhalted)
                return true;
 
-       if (atomic_read(&vcpu->arch.nmi_queued))
+       if ((kvm_test_request(KVM_REQ_NMI, vcpu) ||
+           atomic_read(&vcpu->arch.nmi_queued)) &&
+           kvm_x86_ops->nmi_allowed(vcpu))
                return true;
 
        if (kvm_test_request(KVM_REQ_SMI, vcpu))
-- 
1.8.3.1





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