KVM: APIC: avoid instruction emulation for EOI writes
Instruction emulation for EOI writes can be skipped, since sane
guest simply uses MOV instead of string operations. This is a nice
improvement when guest doesn't support x2apic or hyper-V EOI
support.
a single VM bandwidth is observed with ~8% bandwidth improvement
(7.4Gbps->8Gbps), by saving ~5% cycles from EOI emulation.
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
<Based on earlier work from>:
Signed-off-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 57dcbd4..52645f2 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -864,6 +864,15 @@
return 0;
}
+void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu)
+{
+ struct kvm_lapic *apic = vcpu->arch.apic;
+
+ if (apic)
+ apic_reg_write(vcpu->arch.apic, APIC_EOI, 0);
+}
+EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi);
+
void kvm_free_lapic(struct kvm_vcpu *vcpu)
{
if (!vcpu->arch.apic)
