KVM: only sync when attention bits set

Commit eb0dc6d0368072236dcd086d7fdc17fd3c4574d4 introduced apic
attention bitmask but kvm still syncs lapic unconditionally.
As that commit suggested and in anticipation of adding more attention
bits, only sync lapic if(apic_attention).

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6ed5983f78ff..c1f870690a64 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5388,7 +5388,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
         if (unlikely(vcpu->arch.tsc_always_catchup))
                 kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
 
-        kvm_lapic_sync_from_vapic(vcpu);
+        if (vcpu->arch.apic_attention)
+                kvm_lapic_sync_from_vapic(vcpu);
 
         r = kvm_x86_ops->handle_exit(vcpu);
 out: