[Qemu-devel] [PATCH v3] KVM: x86: Fix nmi injection failure when vcpu got blocked

[Zhuangyanying]

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 nmi_pending, and testing KVM_REQ_NMI replaces nmi_queued
in vm_vcpu_has_events().

Do the same change for SMIs.

Signed-off-by: Zhuang Yanying <address@hidden>
---
v1->v2
  - simplify message. The complete description is here:
    http://www.spinics.net/lists/kvm/msg150380.html
  - Testing KVM_REQ_NMI replaces nmi_pending.
  - Add Testing kvm_x86_ops->nmi_allowed(vcpu).
v2->v3
  - Testing KVM_REQ_NMI replaces nmi_queued, not nmi_pending.
  - Do the same change for SMIs. 
---
 arch/x86/kvm/x86.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 02363e3..a2cd099 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8394,10 +8394,13 @@ 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) ||
+           (vcpu->arch.nmi_pending &&
+            kvm_x86_ops->nmi_allowed(vcpu)))
                return true;
 
-       if (kvm_test_request(KVM_REQ_SMI, vcpu))
+       if (kvm_test_request(KVM_REQ_SMI, vcpu) ||
+           (vcpu->arch.smi_pending && !is_smm(vcpu)))
                return true;
 
        if (kvm_arch_interrupt_allowed(vcpu) &&
-- 
1.8.3.1