From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Optimizing posted-interrupt delivery especially for the timer fastpath
scenario, I observe kvm_x86_ops.deliver_posted_interrupt() has more latency
then vmx_sync_pir_to_irr() in the case of timer fastpath scenario, since
it needs to wait vmentry, after that it can handle external interrupt, ack
the notification vector, read posted-interrupt descriptor etc, it is slower
than evaluate and delivery during vmentry immediately approach. Let's skip
sending interrupt to notify target pCPU and replace by vmx_sync_pir_to_irr()
before each cont_run.
Tested-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Cc: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 9 ++++++---
virt/kvm/kvm_main.c | 1 +
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5c21027..d21b66b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3909,8 +3909,9 @@ static int vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
if (pi_test_and_set_on(&vmx->pi_desc))
return 0;
- if (!kvm_vcpu_trigger_posted_interrupt(vcpu, false))
- kvm_vcpu_kick(vcpu);
+ if (vcpu != kvm_get_running_vcpu() &&
+ !kvm_vcpu_trigger_posted_interrupt(vcpu, false))
+ kvm_vcpu_kick(vcpu);
return 0;
}
@@ -6757,8 +6758,10 @@ static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (!kvm_need_cancel_enter_guest(vcpu)) {
exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
/* static call is better with retpolines */
- if (exit_fastpath == EXIT_FASTPATH_CONT_RUN)
+ if (exit_fastpath == EXIT_FASTPATH_CONT_RUN) {
+ vmx_sync_pir_to_irr(vcpu);
goto cont_run;
+ }
}
return exit_fastpath;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e7436d0..6a289d1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4633,6 +4633,7 @@ struct kvm_vcpu *kvm_get_running_vcpu(void)
return vcpu;
}
+EXPORT_SYMBOL_GPL(kvm_get_running_vcpu);
/**
* kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
--
2.7.4
