From: Wanpeng Li <[email protected]> While optimizing posted-interrupt delivery especially for the timer fastpath scenario, I measured kvm_x86_ops.deliver_posted_interrupt() to introduce substantial latency because the processor has to perform all vmentry tasks, ack the posted interrupt notification vector, read the posted-interrupt descriptor etc.
This is not only slow, it is also unnecessary when delivering an interrupt to the current CPU (as is the case for the LAPIC timer) because PIR->IRR and IRR->RVI synchronization is already performed on vmentry Therefore skip kvm_vcpu_trigger_posted_interrupt in this case, and instead do vmx_sync_pir_to_irr() on the EXIT_FASTPATH_REENTER_GUEST fastpath as well. Tested-by: Haiwei Li <[email protected]> Cc: Haiwei Li <[email protected]> Suggested-by: Paolo Bonzini <[email protected]> Signed-off-by: Wanpeng Li <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> --- arch/x86/kvm/vmx/vmx.c | 4 +++- virt/kvm/kvm_main.c | 1 + 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 215ae9682da1..b980481436e9 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3928,7 +3928,8 @@ 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; @@ -6803,6 +6804,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) * but it would incur the cost of a retpoline for now. * Revisit once static calls are available. */ + vmx_sync_pir_to_irr(vcpu); goto reenter_guest; } exit_fastpath = EXIT_FASTPATH_EXIT_HANDLED; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 825d501df158..7f675d525981 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4638,6 +4638,7 @@ 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. -- 2.18.2
