KVM: Report IRQ injection status to userspace.

IRQ injection status is either -1 (if there was no CPU found
that should except the interrupt because IRQ was masked or
ioapic was misconfigured or ...) or >= 0 in that case the
number indicates to how many CPUs interrupt was injected.
If the value is 0 it means that the interrupt was coalesced
and probably should be reinjected.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 25 insertions, 8 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 55fd4c5fd388..f0faf58044ff 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -616,7 +616,7 @@ void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
 void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long cr2,
                            u32 error_code);
 
-void kvm_pic_set_irq(void *opaque, int irq, int level);
+int kvm_pic_set_irq(void *opaque, int irq, int level);
 
 void kvm_inject_nmi(struct kvm_vcpu *vcpu);
 
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 93160375c841..b4e662e94ddc 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -77,12 +77,13 @@ void kvm_pic_clear_isr_ack(struct kvm *kvm)
 /*
  * set irq level. If an edge is detected, then the IRR is set to 1
  */
-static inline void pic_set_irq1(struct kvm_kpic_state *s, int irq, int level)
+static inline int pic_set_irq1(struct kvm_kpic_state *s, int irq, int level)
 {
-        int mask;
+        int mask, ret = 1;
         mask = 1 << irq;
         if (s->elcr & mask)     /* level triggered */
                 if (level) {
+                        ret = !(s->irr & mask);
                         s->irr |= mask;
                         s->last_irr |= mask;
                 } else {
@@ -91,11 +92,15 @@ static inline void pic_set_irq1(struct kvm_kpic_state *s, int irq, int level)
                 }
         else    /* edge triggered */
                 if (level) {
-                        if ((s->last_irr & mask) == 0)
+                        if ((s->last_irr & mask) == 0) {
+                                ret = !(s->irr & mask);
                                 s->irr |= mask;
+                        }
                         s->last_irr |= mask;
                 } else
                         s->last_irr &= ~mask;
+
+        return (s->imr & mask) ? -1 : ret;
 }
 
 /*
@@ -172,16 +177,19 @@ void kvm_pic_update_irq(struct kvm_pic *s)
         pic_unlock(s);
 }
 
-void kvm_pic_set_irq(void *opaque, int irq, int level)
+int kvm_pic_set_irq(void *opaque, int irq, int level)
 {
         struct kvm_pic *s = opaque;
+        int ret = -1;
 
         pic_lock(s);
         if (irq >= 0 && irq < PIC_NUM_PINS) {
-                pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);
+                ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);
                 pic_update_irq(s);
         }
         pic_unlock(s);
+
+        return ret;
 }
 
 /*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 05d7be89b5eb..e4db5be7c953 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1019,6 +1019,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_MP_STATE:
         case KVM_CAP_SYNC_MMU:
         case KVM_CAP_REINJECT_CONTROL:
+        case KVM_CAP_IRQ_INJECT_STATUS:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO:
@@ -1877,6 +1878,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
         create_pit_unlock:
                 mutex_unlock(&kvm->lock);
                 break;
+        case KVM_IRQ_LINE_STATUS:
         case KVM_IRQ_LINE: {
                 struct kvm_irq_level irq_event;
 
@@ -1884,10 +1886,17 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 if (copy_from_user(&irq_event, argp, sizeof irq_event))
                         goto out;
                 if (irqchip_in_kernel(kvm)) {
+                        __s32 status;
                         mutex_lock(&kvm->lock);
-                        kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID,
-                                    irq_event.irq, irq_event.level);
+                        status = kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID,
+                                        irq_event.irq, irq_event.level);
                         mutex_unlock(&kvm->lock);
+                        if (ioctl == KVM_IRQ_LINE_STATUS) {
+                                irq_event.status = status;
+                                if (copy_to_user(argp, &irq_event,
+                                                        sizeof irq_event))
+                                        goto out;
+                        }
                         r = 0;
                 }
                 break;