On Fri, Apr 24, 2020 at 02:22:42PM +0800, Wanpeng Li wrote:
> 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))
Bad indentation.
> + 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
>
