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 reenter guest.
Tested-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Cc: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 12 ++++++++----
virt/kvm/kvm_main.c | 1 +
2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 24cadf4..ce19b0e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3909,7 +3909,8 @@ 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))
+ if (vcpu != kvm_get_running_vcpu() &&
+ !kvm_vcpu_trigger_posted_interrupt(vcpu, false))
kvm_vcpu_kick(vcpu);
return 0;
@@ -6777,9 +6778,12 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx_complete_interrupts(vmx);
exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
- if (exit_fastpath == EXIT_FASTPATH_REENTER_GUEST &&
- kvm_vcpu_exit_request(vcpu))
- exit_fastpath = EXIT_FASTPATH_NOP;
+ if (exit_fastpath == EXIT_FASTPATH_REENTER_GUEST) {
+ if (!kvm_vcpu_exit_request(vcpu))
+ vmx_sync_pir_to_irr(vcpu);
+ else
+ exit_fastpath = EXIT_FASTPATH_NOP;
+ }
return exit_fastpath;
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 33e1eee..2482f3c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4644,6 +4644,7 @@ 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
