diff mbox series

[2/3] KVM: X86: Narrow down the IPI fastpath to single target IPI

Message ID 1585189202-1708-3-git-send-email-wanpengli@tencent.com (mailing list archive)
State New, archived
Headers show
Series KVM: X86: Single target IPI fastpath enhancement | expand

Commit Message

Wanpeng Li March 26, 2020, 2:20 a.m. UTC 
From: Wanpeng Li <wanpengli@tencent.com>

The original single target IPI fastpath patch forgot to filter the 
ICR destination shorthand field. Multicast IPI is not suitable for 
this feature since wakeup the multiple sleeping vCPUs will extend 
the interrupt disabled time, it especially worse in the over-subscribe 
and VM has a little bit more vCPUs scenario. Let's narrow it down to 
single target IPI.

Two VMs, each is 76 vCPUs, one running 'ebizzy -M', the other 
running cyclictest on all vCPUs, w/ this patch, the avg score 
of cyclictest can improve more than 5%. (pv tlb, pv ipi, pv 
sched yield are disabled during testing to avoid the disturb).

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kvm/x86.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9232b15..50ef1c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1554,7 +1554,10 @@  EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);
  */
 static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data)
 {
-	if (lapic_in_kernel(vcpu) && apic_x2apic_mode(vcpu->arch.apic) &&
+	if (!lapic_in_kernel(vcpu) || !apic_x2apic_mode(vcpu->arch.apic))
+		return 1;
+
+	if (((data & APIC_SHORT_MASK) == APIC_DEST_NOSHORT) &&
 		((data & APIC_DEST_MASK) == APIC_DEST_PHYSICAL) &&
 		((data & APIC_MODE_MASK) == APIC_DM_FIXED)) {