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, 45 insertions, 21 deletions

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 1c986ac59ad6..c3b99def9cbc 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -83,19 +83,22 @@ static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
         return result;
 }
 
-static void ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
+static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
 {
         union ioapic_redir_entry *pent;
+        int injected = -1;
 
         pent = &ioapic->redirtbl[idx];
 
         if (!pent->fields.mask) {
-                int injected = ioapic_deliver(ioapic, idx);
+                injected = ioapic_deliver(ioapic, idx);
                 if (injected && pent->fields.trig_mode == IOAPIC_LEVEL_TRIG)
                         pent->fields.remote_irr = 1;
         }
         if (!pent->fields.trig_mode)
                 ioapic->irr &= ~(1 << idx);
+
+        return injected;
 }
 
 static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
@@ -207,7 +210,7 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
         u8 trig_mode = ioapic->redirtbl[irq].fields.trig_mode;
         u32 deliver_bitmask;
         struct kvm_vcpu *vcpu;
-        int vcpu_id, r = 0;
+        int vcpu_id, r = -1;
 
         ioapic_debug("dest=%x dest_mode=%x delivery_mode=%x "
                      "vector=%x trig_mode=%x\n",
@@ -247,7 +250,9 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
                         deliver_bitmask &= ~(1 << vcpu_id);
                         vcpu = ioapic->kvm->vcpus[vcpu_id];
                         if (vcpu) {
-                                r = ioapic_inj_irq(ioapic, vcpu, vector,
+                                if (r < 0)
+                                        r = 0;
+                                r += ioapic_inj_irq(ioapic, vcpu, vector,
                                                trig_mode, delivery_mode);
                         }
                 }
@@ -258,8 +263,10 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
                                 continue;
                         deliver_bitmask &= ~(1 << vcpu_id);
                         vcpu = ioapic->kvm->vcpus[vcpu_id];
-                        if (vcpu)
+                        if (vcpu) {
                                 ioapic_inj_nmi(vcpu);
+                                r = 1;
+                        }
                         else
                                 ioapic_debug("NMI to vcpu %d failed\n",
                                                 vcpu->vcpu_id);
@@ -273,11 +280,12 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
         return r;
 }
 
-void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
+int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 {
         u32 old_irr = ioapic->irr;
         u32 mask = 1 << irq;
         union ioapic_redir_entry entry;
+        int ret = 1;
 
         if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
                 entry = ioapic->redirtbl[irq];
@@ -288,9 +296,10 @@ void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
                         ioapic->irr |= mask;
                         if ((!entry.fields.trig_mode && old_irr != ioapic->irr)
                             || !entry.fields.remote_irr)
-                                ioapic_service(ioapic, irq);
+                                ret = ioapic_service(ioapic, irq);
                 }
         }
+        return ret;
 }
 
 static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int pin,
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 49c9581d2586..a34bd5e6436b 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -83,7 +83,7 @@ struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
                                        unsigned long bitmap);
 void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
 int kvm_ioapic_init(struct kvm *kvm);
-void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
+int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic);
 u32 kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
                                 u8 dest_mode);
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 6bc7439eff6e..be8aba791554 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -29,22 +29,24 @@
 
 #include "ioapic.h"
 
-static void kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
-                            struct kvm *kvm, int level)
+static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
+                           struct kvm *kvm, int level)
 {
 #ifdef CONFIG_X86
-        kvm_pic_set_irq(pic_irqchip(kvm), e->irqchip.pin, level);
+        return kvm_pic_set_irq(pic_irqchip(kvm), e->irqchip.pin, level);
+#else
+        return -1;
 #endif
 }
 
-static void kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
-                               struct kvm *kvm, int level)
+static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
+                              struct kvm *kvm, int level)
 {
-        kvm_ioapic_set_irq(kvm->arch.vioapic, e->irqchip.pin, level);
+        return kvm_ioapic_set_irq(kvm->arch.vioapic, e->irqchip.pin, level);
 }
 
-static void kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
-                        struct kvm *kvm, int level)
+static int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
+                       struct kvm *kvm, int level)
 {
         int vcpu_id;
         struct kvm_vcpu *vcpu;
@@ -88,13 +90,20 @@ static void kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
         default:
                 break;
         }
+        return 1;
 }
 
-/* This should be called with the kvm->lock mutex held */
-void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
+/* This should be called with the kvm->lock mutex held
+ * Return value:
+ *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
+ *  = 0   Interrupt was coalesced (previous irq is still pending)
+ *  > 0   Number of CPUs interrupt was delivered to
+ */
+int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
 {
         struct kvm_kernel_irq_routing_entry *e;
         unsigned long *irq_state, sig_level;
+        int ret = -1;
 
         if (irq < KVM_IOAPIC_NUM_PINS) {
                 irq_state = (unsigned long *)&kvm->arch.irq_states[irq];
@@ -113,8 +122,14 @@ void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
          * writes to the unused one.
          */
         list_for_each_entry(e, &kvm->irq_routing, link)
-                if (e->gsi == irq)
-                        e->set(e, kvm, sig_level);
+                if (e->gsi == irq) {
+                        int r = e->set(e, kvm, sig_level);
+                        if (r < 0)
+                                continue;
+
+                        ret = r + ((ret < 0) ? 0 : ret);
+                }
+        return ret;
 }
 
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
@@ -232,7 +247,7 @@ int setup_routing_entry(struct kvm_kernel_irq_routing_entry *e,
                         e->set = kvm_set_pic_irq;
                         break;
                 case KVM_IRQCHIP_PIC_SLAVE:
-                                e->set = kvm_set_pic_irq;
+                        e->set = kvm_set_pic_irq;
                         delta = 8;
                         break;
                 case KVM_IRQCHIP_IOAPIC: