| Message ID | 1573283135-5502-2-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] KVM: X86: Single target IPI fastpath | expand |
On 09/11/19 08:05, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > After disabling mwait/halt/pause vmexits, RESCHEDULE_VECTOR and > CALL_FUNCTION_SINGLE_VECTOR etc IPI is one of the main remaining > cause of vmexits observed in product environment which can't be > optimized by PV IPIs. This patch is the follow-up on commit > 0e6d242eccdb (KVM: LAPIC: Micro optimize IPI latency), to optimize > redundancy logic before fixed mode ipi is delivered in the fast > path. > > - broadcast handling needs to go slow path, so the delivery mode repair > can be delayed to before slow path. I agree with this part, but is the cost of the irq->shorthand check really measurable? Paolo > - self-IPI will not be intervened by hypervisor any more after APICv is > introduced and the boxes support APICv are popular now. In addition, > kvm_apic_map_get_dest_lapic() can handle the self-IPI, so there is no > need a shortcut for the non-APICv case. > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/kvm/irq_comm.c | 6 +++--- > arch/x86/kvm/lapic.c | 5 ----- > 2 files changed, 3 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c > index 8ecd48d..aa88156 100644 > --- a/arch/x86/kvm/irq_comm.c > +++ b/arch/x86/kvm/irq_comm.c > @@ -52,15 +52,15 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]; > unsigned int dest_vcpus = 0; > > + if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) > + return r; > + > if (irq->dest_mode == 0 && irq->dest_id == 0xff && > kvm_lowest_prio_delivery(irq)) { > printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n"); > irq->delivery_mode = APIC_DM_FIXED; > } > > - if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) > - return r; > - > memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap)); > > kvm_for_each_vcpu(i, vcpu, kvm) { > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index b29d00b..ea936fa 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -951,11 +951,6 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src, > > *r = -1; > > - if (irq->shorthand == APIC_DEST_SELF) { > - *r = kvm_apic_set_irq(src->vcpu, irq, dest_map); > - return true; > - } > - > rcu_read_lock(); > map = rcu_dereference(kvm->arch.apic_map); > >
On Tue, 12 Nov 2019 at 05:59, Paolo Bonzini <pbonzini@redhat.com> wrote: > > On 09/11/19 08:05, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > After disabling mwait/halt/pause vmexits, RESCHEDULE_VECTOR and > > CALL_FUNCTION_SINGLE_VECTOR etc IPI is one of the main remaining > > cause of vmexits observed in product environment which can't be > > optimized by PV IPIs. This patch is the follow-up on commit > > 0e6d242eccdb (KVM: LAPIC: Micro optimize IPI latency), to optimize > > redundancy logic before fixed mode ipi is delivered in the fast > > path. > > > > - broadcast handling needs to go slow path, so the delivery mode repair > > can be delayed to before slow path. > > I agree with this part, but is the cost of the irq->shorthand check > really measurable? I can drop the second part for v2. Wanpeng
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c index 8ecd48d..aa88156 100644 --- a/arch/x86/kvm/irq_comm.c +++ b/arch/x86/kvm/irq_comm.c @@ -52,15 +52,15 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]; unsigned int dest_vcpus = 0; + if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) + return r; + if (irq->dest_mode == 0 && irq->dest_id == 0xff && kvm_lowest_prio_delivery(irq)) { printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n"); irq->delivery_mode = APIC_DM_FIXED; } - if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) - return r; - memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap)); kvm_for_each_vcpu(i, vcpu, kvm) { diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index b29d00b..ea936fa 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -951,11 +951,6 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src, *r = -1; - if (irq->shorthand == APIC_DEST_SELF) { - *r = kvm_apic_set_irq(src->vcpu, irq, dest_map); - return true; - } - rcu_read_lock(); map = rcu_dereference(kvm->arch.apic_map);