KVM: round robin for APIC lowest priority delivery mode

Signed-off-by: Qing He <qing.he@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 29 insertions, 5 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index f8fe87d3ddbd..dbb929d8a31e 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -413,6 +413,7 @@ struct kvm {
         struct kvm_io_bus pio_bus;
         struct kvm_pic *vpic;
         struct kvm_ioapic *vioapic;
+        int round_robin_prev_vcpu;
 };
 
 static inline struct kvm_pic *pic_irqchip(struct kvm *kvm)
diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c
index 01e769672dcc..ca1db3852ace 100644
--- a/drivers/kvm/lapic.c
+++ b/drivers/kvm/lapic.c
@@ -371,12 +371,35 @@ struct kvm_lapic *kvm_apic_round_robin(struct kvm *kvm, u8 vector,
                                        unsigned long bitmap)
 {
         int vcpu_id;
+        int last;
+        int next;
+        struct kvm_lapic *apic;
+
+        last = kvm->round_robin_prev_vcpu;
+        next = last;
+
+        do {
+                if (++next == KVM_MAX_VCPUS)
+                        next = 0;
+                if (kvm->vcpus[next] == NULL || !test_bit(next, &bitmap))
+                        continue;
+                apic = kvm->vcpus[next]->apic;
+                if (apic && apic_enabled(apic))
+                        break;
+                apic = NULL;
+        } while (next != last);
+        kvm->round_robin_prev_vcpu = next;
+
+        if (!apic) {
+                vcpu_id = ffs(bitmap) - 1;
+                if (vcpu_id < 0) {
+                        vcpu_id = 0;
+                        printk(KERN_DEBUG "vcpu not ready for apic_round_robin\n");
+                }
+                apic = kvm->vcpus[vcpu_id]->apic;
+        }
 
-        /* TODO for real round robin */
-        vcpu_id = fls(bitmap) - 1;
-        if (vcpu_id < 0)
-                printk(KERN_DEBUG "vcpu not ready for apic_round_robin\n");
-        return kvm->vcpus[vcpu_id]->apic;
+        return apic;
 }
 
 static void apic_set_eoi(struct kvm_lapic *apic)