From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
This patch implements handle preemption timer fastpath, after timer fire
due to VMX-preemption timer counts down to zero, handle it as soon as
possible and vmentry immediately without checking various kvm stuff when
possible.
Testing on SKX Server.
cyclictest in guest(w/o mwait exposed, adaptive advance lapic timer is default -1):
5540.5ns -> 4602ns 17%
kvm-unit-test/vmexit.flat:
w/o avanced timer:
tscdeadline_immed: 2885 -> 2431.25 15.7%
tscdeadline: 5668.75 -> 5188.5 8.4%
w/ adaptive advance timer default -1:
tscdeadline_immed: 2965.25 -> 2520 15.0%
tscdeadline: 4663.75 -> 4537 2.7%
Tested-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Cc: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d21b66b..028967a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6560,12 +6560,28 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
}
}
+static enum exit_fastpath_completion handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ if (!vmx->req_immediate_exit &&
+ !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) {
+ kvm_lapic_expired_hv_timer(vcpu);
+ trace_kvm_exit(EXIT_REASON_PREEMPTION_TIMER, vcpu, KVM_ISA_VMX);
+ return EXIT_FASTPATH_CONT_RUN;
+ }
+
+ return EXIT_FASTPATH_NONE;
+}
+
static enum exit_fastpath_completion vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
{
if (!is_guest_mode(vcpu) && vcpu->arch.apicv_active) {
switch (to_vmx(vcpu)->exit_reason) {
case EXIT_REASON_MSR_WRITE:
return handle_fastpath_set_msr_irqoff(vcpu);
+ case EXIT_REASON_PREEMPTION_TIMER:
+ return handle_fastpath_preemption_timer(vcpu);
default:
return EXIT_FASTPATH_NONE;
}
--
2.7.4
