KVM: Do not report TPR write to userspace if new value bigger or equal to a previous one.
Saves many exits to userspace in a case of IRQ chip in userspace.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9162b4c..51f804c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2724,13 +2724,18 @@
kvm_set_cr4(vcpu, kvm_register_read(vcpu, reg));
skip_emulated_instruction(vcpu);
return 1;
- case 8:
- kvm_set_cr8(vcpu, kvm_register_read(vcpu, reg));
- skip_emulated_instruction(vcpu);
- if (irqchip_in_kernel(vcpu->kvm))
- return 1;
- kvm_run->exit_reason = KVM_EXIT_SET_TPR;
- return 0;
+ case 8: {
+ u8 cr8_prev = kvm_get_cr8(vcpu);
+ u8 cr8 = kvm_register_read(vcpu, reg);
+ kvm_set_cr8(vcpu, cr8);
+ skip_emulated_instruction(vcpu);
+ if (irqchip_in_kernel(vcpu->kvm))
+ return 1;
+ if (cr8_prev <= cr8)
+ return 1;
+ kvm_run->exit_reason = KVM_EXIT_SET_TPR;
+ return 0;
+ }
};
break;
case 2: /* clts */