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authorWanpeng Li <wanpengli@tencent.com>2020-04-28 14:23:27 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2020-05-15 12:26:20 -0400
commit379a3c8ee44440d5afa505230ed8cb5b0d0e314b (patch)
tree85d3010294ab19df707ea05be9b9863c40e14f02
parent404d5d7bff0d419fe11c7eaebca9ec8f25258f95 (diff)
KVM: VMX: Optimize posted-interrupt delivery for timer fastpath
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 <lihaiwei@tencent.com> Cc: Haiwei Li <lihaiwei@tencent.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Message-Id: <1588055009-12677-6-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/vmx/vmx.c5
-rw-r--r--virt/kvm/kvm_main.c1
2 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c7730d3aa706..8d881fcf648e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3936,7 +3936,8 @@ 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;
@@ -6812,6 +6813,8 @@ reenter_guest:
* but it would incur the cost of a retpoline for now.
* Revisit once static calls are available.
*/
+ if (vcpu->arch.apicv_active)
+ 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 bef3d8d40685..11844fad60fd 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4646,6 +4646,7 @@ 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.

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