KVM: change the way how lowest priority vcpu is calculated

The new way does not require additional loop over vcpus to calculate
the one with lowest priority as one is chosen during delivery bitmap
construction.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 6 insertions, 37 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 998862a3c267..814466f455d9 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -338,8 +338,9 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
         struct kvm_vcpu *vcpu = apic->vcpu;
 
         switch (delivery_mode) {
-        case APIC_DM_FIXED:
         case APIC_DM_LOWEST:
+                vcpu->arch.apic_arb_prio++;
+        case APIC_DM_FIXED:
                 /* FIXME add logic for vcpu on reset */
                 if (unlikely(!apic_enabled(apic)))
                         break;
@@ -416,43 +417,9 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
         return result;
 }
 
-static struct kvm_lapic *kvm_apic_round_robin(struct kvm *kvm, u8 vector,
-                                       unsigned long *bitmap)
+int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
 {
-        int last;
-        int next;
-        struct kvm_lapic *apic = NULL;
-
-        last = kvm->arch.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]->arch.apic;
-                if (apic && apic_enabled(apic))
-                        break;
-                apic = NULL;
-        } while (next != last);
-        kvm->arch.round_robin_prev_vcpu = next;
-
-        if (!apic)
-                printk(KERN_DEBUG "vcpu not ready for apic_round_robin\n");
-
-        return apic;
-}
-
-struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
-                unsigned long *bitmap)
-{
-        struct kvm_lapic *apic;
-
-        apic = kvm_apic_round_robin(kvm, vector, bitmap);
-        if (apic)
-                return apic->vcpu;
-        return NULL;
+        return vcpu1->arch.apic_arb_prio - vcpu2->arch.apic_arb_prio;
 }
 
 static void apic_set_eoi(struct kvm_lapic *apic)
@@ -908,6 +875,8 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
                 vcpu->arch.apic_base |= MSR_IA32_APICBASE_BSP;
         apic_update_ppr(apic);
 
+        vcpu->arch.apic_arb_prio = 0;
+
         apic_debug(KERN_INFO "%s: vcpu=%p, id=%d, base_msr="
                    "0x%016" PRIx64 ", base_address=0x%0lx.\n", __func__,
                    vcpu, kvm_apic_id(apic),