path: root/virt/kvm/ioapic.c
diff options
authorMichael S. Tsirkin <mst@redhat.com>2012-04-11 18:49:55 +0300
committerMarcelo Tosatti <mtosatti@redhat.com>2012-04-16 20:36:38 -0300
commita0c9a822bf37e6282eb6006b407ec5aec22e08fb (patch)
tree62e0ba3e3b031ded8187b1c37681015ec920ebe2 /virt/kvm/ioapic.c
parente59717550e5cf0e7159c5b7af1d1ead35fef49dd (diff)
KVM: dont clear TMR on EOI
Intel spec says that TMR needs to be set/cleared when IRR is set, but kvm also clears it on EOI. I did some tests on a real (AMD based) system, and I see same TMR values both before and after EOI, so I think it's a minor bug in kvm. This patch fixes TMR to be set/cleared on IRR set only as per spec. And now that we don't clear TMR, we can save an atomic read of TMR on EOI that's not propagated to ioapic, by checking whether ioapic needs a specific vector first and calculating the mode afterwards. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'virt/kvm/ioapic.c')
1 files changed, 7 insertions, 3 deletions
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index dcaf272c26c..26fd54dc459 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -254,13 +254,17 @@ static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
+bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector)
+ struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+ smp_rmb();
+ return test_bit(vector, ioapic->handled_vectors);
void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
struct kvm_ioapic *ioapic = kvm->arch.vioapic;
- smp_rmb();
- if (!test_bit(vector, ioapic->handled_vectors))
- return;
__kvm_ioapic_update_eoi(ioapic, vector, trigger_mode);