From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
"Wanpeng Li" <wanpengli@tencent.com>,
"Jim Mattson" <jmattson@google.com>,
"Joerg Roedel" <joro@8bytes.org>
Subject: [PATCH RESEND 3/5] KVM: LAPIC: Micro optimize IPI latency
Date: Fri, 6 Sep 2019 09:30:02 +0800 [thread overview]
Message-ID: <1567733404-7759-3-git-send-email-wanpengli@tencent.com> (raw)
In-Reply-To: <1567733404-7759-1-git-send-email-wanpengli@tencent.com>
From: Wanpeng Li <wanpengli@tencent.com>
This patch optimizes the virtual IPI emulation sequence:
write ICR2 write ICR2
write ICR read ICR2
read ICR ==> send virtual IPI
read ICR2 write ICR
send virtual IPI
It can reduce kvm-unit-tests/vmexit.flat IPI testing latency(from sender
send IPI to sender receive the ACK) from 3319 cycles to 3203 cycles on
SKylake server.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/lapic.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 12ade70..34fd299 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1200,10 +1200,8 @@ void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector)
}
EXPORT_SYMBOL_GPL(kvm_apic_set_eoi_accelerated);
-static void apic_send_ipi(struct kvm_lapic *apic)
+static void apic_send_ipi(struct kvm_lapic *apic, u32 icr_low, u32 icr_high)
{
- u32 icr_low = kvm_lapic_get_reg(apic, APIC_ICR);
- u32 icr_high = kvm_lapic_get_reg(apic, APIC_ICR2);
struct kvm_lapic_irq irq;
irq.vector = icr_low & APIC_VECTOR_MASK;
@@ -1940,8 +1938,9 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
}
case APIC_ICR:
/* No delay here, so we always clear the pending bit */
- kvm_lapic_set_reg(apic, APIC_ICR, val & ~(1 << 12));
- apic_send_ipi(apic);
+ val &= ~(1 << 12);
+ apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2));
+ kvm_lapic_set_reg(apic, APIC_ICR, val);
break;
case APIC_ICR2:
--
2.7.4
next prev parent reply other threads:[~2019-09-06 1:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 1:30 [PATCH RESEND v3 1/5] KVM: LAPIC: Tune lapic_timer_advance_ns smoothly Wanpeng Li
2019-09-06 1:30 ` [PATCH RESEND v3 2/5] KVM: LAPIC: Periodically revaluate to get conservative lapic_timer_advance_ns Wanpeng Li
2019-09-06 1:30 ` Wanpeng Li [this message]
2019-09-06 1:30 ` [PATCH RESEND 4/5] KVM: VMX: Stop the preemption timer during vCPU reset Wanpeng Li
2019-09-06 1:30 ` [PATCH v2 5/5] KVM: hyperv: Fix Direct Synthetic timers assert an interrupt w/o lapic_in_kernel Wanpeng Li
2019-09-11 16:26 ` Paolo Bonzini
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