KVM: SVM: Improve nested interrupt injection

While trying to get Hyper-V running, I realized that the interrupt injection
mechanisms that are in place right now are not 100% correct.

This patch makes nested SVM's interrupt injection behave more like on a
real machine.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 24 insertions, 15 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index be699795d70..45666618377 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1612,7 +1612,8 @@ static int nested_svm_vmexit_real(struct vcpu_svm *svm, void *arg1,
         /* Kill any pending exceptions */
         if (svm->vcpu.arch.exception.pending == true)
                 nsvm_printk("WARNING: Pending Exception\n");
-        svm->vcpu.arch.exception.pending = false;
+        kvm_clear_exception_queue(&svm->vcpu);
+        kvm_clear_interrupt_queue(&svm->vcpu);
 
         /* Restore selected save entries */
         svm->vmcb->save.es = hsave->save.es;
@@ -1680,7 +1681,8 @@ static int nested_svm_vmrun(struct vcpu_svm *svm, void *arg1,
         svm->nested_vmcb = svm->vmcb->save.rax;
 
         /* Clear internal status */
-        svm->vcpu.arch.exception.pending = false;
+        kvm_clear_exception_queue(&svm->vcpu);
+        kvm_clear_interrupt_queue(&svm->vcpu);
 
         /* Save the old vmcb, so we don't need to pick what we save, but
            can restore everything when a VMEXIT occurs */
@@ -2362,21 +2364,14 @@ static inline void svm_inject_irq(struct vcpu_svm *svm, int irq)
                 ((/*control->int_vector >> 4*/ 0xf) << V_INTR_PRIO_SHIFT);
 }
 
-static void svm_queue_irq(struct kvm_vcpu *vcpu, unsigned nr)
-{
-        struct vcpu_svm *svm = to_svm(vcpu);
-
-        svm->vmcb->control.event_inj = nr |
-                SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
-}
-
 static void svm_set_irq(struct kvm_vcpu *vcpu)
 {
         struct vcpu_svm *svm = to_svm(vcpu);
 
-        nested_svm_intr(svm);
+        BUG_ON(!(svm->vcpu.arch.hflags & HF_GIF_MASK));
 
-        svm_queue_irq(vcpu, vcpu->arch.interrupt.nr);
+        svm->vmcb->control.event_inj = vcpu->arch.interrupt.nr |
+                SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
 }
 
 static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
@@ -2404,13 +2399,25 @@ static int svm_interrupt_allowed(struct kvm_vcpu *vcpu)
         struct vmcb *vmcb = svm->vmcb;
         return (vmcb->save.rflags & X86_EFLAGS_IF) &&
                 !(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
-                (svm->vcpu.arch.hflags & HF_GIF_MASK);
+                (svm->vcpu.arch.hflags & HF_GIF_MASK) &&
+                !is_nested(svm);
 }
 
 static void enable_irq_window(struct kvm_vcpu *vcpu)
 {
-        svm_set_vintr(to_svm(vcpu));
-        svm_inject_irq(to_svm(vcpu), 0x0);
+        struct vcpu_svm *svm = to_svm(vcpu);
+        nsvm_printk("Trying to open IRQ window\n");
+
+        nested_svm_intr(svm);
+
+        /* In case GIF=0 we can't rely on the CPU to tell us when
+         * GIF becomes 1, because that's a separate STGI/VMRUN intercept.
+         * The next time we get that intercept, this function will be
+         * called again though and we'll get the vintr intercept. */
+        if (svm->vcpu.arch.hflags & HF_GIF_MASK) {
+                svm_set_vintr(svm);
+                svm_inject_irq(svm, 0x0);
+        }
 }
 
 static void enable_nmi_window(struct kvm_vcpu *vcpu)
@@ -2489,6 +2496,8 @@ static void svm_complete_interrupts(struct vcpu_svm *svm)
         case SVM_EXITINTINFO_TYPE_EXEPT:
                 /* In case of software exception do not reinject an exception
                    vector, but re-execute and instruction instead */
+                if (is_nested(svm))
+                        break;
                 if (kvm_exception_is_soft(vector))
                         break;
                 if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) {