From e1be9ac8e6014a9b0a216aebae7250f9863e9fc3 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 26 Mar 2020 10:20:01 +0800 Subject: [PATCH] KVM: X86: Narrow down the IPI fastpath to single target IPI 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 Message-Id: <1585189202-1708-3-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d65ff20..cf95c36 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)) { -- 2.7.4