KVM: nSVM: avoid loss of pending IRQ/NMI before entering L2

This patch reproduces for nSVM the change that was made for nVMX in
commit b5861e5cf2fc ("KVM: nVMX: Fix loss of pending IRQ/NMI before
entering L2").  While I do not have a test that breaks without it, I
cannot see why it would not be necessary since all events are unblocked
by VMRUN's setting of GIF back to 1.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 80f15a2..c923ad1 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3576,6 +3576,10 @@ static bool nested_vmcb_checks(struct vmcb *vmcb)
 static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
                                 struct vmcb *nested_vmcb, struct kvm_host_map *map)
 {
+       bool evaluate_pending_interrupts =
+               is_intercept(svm, INTERCEPT_VINTR) ||
+               is_intercept(svm, INTERCEPT_IRET);
+
        if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
                svm->vcpu.arch.hflags |= HF_HIF_MASK;
        else
@@ -3662,7 +3666,21 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
 
        svm->nested.vmcb = vmcb_gpa;
 
+       /*
+        * If L1 had a pending IRQ/NMI before executing VMRUN,
+        * which wasn't delivered because it was disallowed (e.g.
+        * interrupts disabled), L0 needs to evaluate if this pending
+        * event should cause an exit from L2 to L1 or be delivered
+        * directly to L2.
+        *
+        * Usually this would be handled by the processor noticing an
+        * IRQ/NMI window request.  However, VMRUN can unblock interrupts
+        * by implicitly setting GIF, so force L0 to perform pending event
+        * evaluation by requesting a KVM_REQ_EVENT.
+        */
        enable_gif(svm);
+       if (unlikely(evaluate_pending_interrupts))
+               kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
 
        mark_all_dirty(svm->vmcb);
 }