[PATCH v2 11/16] Do not report TPR write to userspace if new value bigger or equal to a previous one.

Gleb Natapov
2009-04-21T14:45:16Z

Saves many exits to userspace in a case of IRQ chip in userspace.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
arch/x86/kvm/svm.c | 4 ++++
arch/x86/kvm/vmx.c | 19 ++++++++++++-------
2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 52bd999..9a8eb14 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1853,9 +1853,13 @@ static int emulate_on_interception(struct vcpu_svm *svm,

static int cr8_write_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
{
+ u8 cr8_prev = kvm_get_cr8(&svm->vcpu);
+ /* instruction emulation calls kvm_set_cr8() */
emulate_instruction(&svm->vcpu, NULL, 0, 0, 0);
if (irqchip_in_kernel(svm->vcpu.kvm))
return 1;
+ if (cr8_prev <= kvm_get_cr8(&svm->vcpu))
+ return 1;
kvm_run->exit_reason = KVM_EXIT_SET_TPR;
return 0;
}
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 @@ static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
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 */
--
1.5.6.5