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https://github.com/edk2-porting/linux-next.git
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KVM: LAPIC: Recalculate apic map in batch
In the vCPU reset and set APIC_BASE MSR path, the apic map will be recalculated several times, each time it will consume 10+ us observed by ftrace in my non-overcommit environment since the expensive memory allocate/mutex/rcu etc operations. This patch optimizes it by recaluating apic map in batch, I hope this can benefit the serverless scenario which can frequently create/destroy VMs. Before patch: kvm_lapic_reset ~27us After patch: kvm_lapic_reset ~14us Observed by ftrace, improve ~48%. Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -920,6 +920,7 @@ struct kvm_arch {
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atomic_t vapics_in_nmi_mode;
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struct mutex apic_map_lock;
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struct kvm_apic_map *apic_map;
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bool apic_map_dirty;
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bool apic_access_page_done;
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unsigned long apicv_inhibit_reasons;
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@ -164,14 +164,28 @@ static void kvm_apic_map_free(struct rcu_head *rcu)
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kvfree(map);
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}
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static void recalculate_apic_map(struct kvm *kvm)
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void kvm_recalculate_apic_map(struct kvm *kvm)
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{
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struct kvm_apic_map *new, *old = NULL;
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struct kvm_vcpu *vcpu;
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int i;
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u32 max_id = 255; /* enough space for any xAPIC ID */
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if (!kvm->arch.apic_map_dirty) {
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/*
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* Read kvm->arch.apic_map_dirty before
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* kvm->arch.apic_map
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*/
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smp_rmb();
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return;
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}
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mutex_lock(&kvm->arch.apic_map_lock);
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if (!kvm->arch.apic_map_dirty) {
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/* Someone else has updated the map. */
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mutex_unlock(&kvm->arch.apic_map_lock);
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return;
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}
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kvm_for_each_vcpu(i, vcpu, kvm)
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if (kvm_apic_present(vcpu))
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@ -236,6 +250,12 @@ out:
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old = rcu_dereference_protected(kvm->arch.apic_map,
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lockdep_is_held(&kvm->arch.apic_map_lock));
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rcu_assign_pointer(kvm->arch.apic_map, new);
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/*
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* Write kvm->arch.apic_map before
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* clearing apic->apic_map_dirty
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*/
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smp_wmb();
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kvm->arch.apic_map_dirty = false;
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mutex_unlock(&kvm->arch.apic_map_lock);
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if (old)
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@ -257,20 +277,20 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val)
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else
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static_key_slow_inc(&apic_sw_disabled.key);
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recalculate_apic_map(apic->vcpu->kvm);
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apic->vcpu->kvm->arch.apic_map_dirty = true;
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}
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}
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static inline void kvm_apic_set_xapic_id(struct kvm_lapic *apic, u8 id)
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{
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kvm_lapic_set_reg(apic, APIC_ID, id << 24);
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recalculate_apic_map(apic->vcpu->kvm);
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apic->vcpu->kvm->arch.apic_map_dirty = true;
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}
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static inline void kvm_apic_set_ldr(struct kvm_lapic *apic, u32 id)
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{
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kvm_lapic_set_reg(apic, APIC_LDR, id);
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recalculate_apic_map(apic->vcpu->kvm);
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apic->vcpu->kvm->arch.apic_map_dirty = true;
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}
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static inline u32 kvm_apic_calc_x2apic_ldr(u32 id)
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@ -286,7 +306,7 @@ static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u32 id)
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kvm_lapic_set_reg(apic, APIC_ID, id);
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kvm_lapic_set_reg(apic, APIC_LDR, ldr);
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recalculate_apic_map(apic->vcpu->kvm);
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apic->vcpu->kvm->arch.apic_map_dirty = true;
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}
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static inline int apic_lvt_enabled(struct kvm_lapic *apic, int lvt_type)
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@ -1906,7 +1926,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
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case APIC_DFR:
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if (!apic_x2apic_mode(apic)) {
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kvm_lapic_set_reg(apic, APIC_DFR, val | 0x0FFFFFFF);
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recalculate_apic_map(apic->vcpu->kvm);
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apic->vcpu->kvm->arch.apic_map_dirty = true;
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} else
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ret = 1;
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break;
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@ -2012,6 +2032,8 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
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break;
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}
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kvm_recalculate_apic_map(apic->vcpu->kvm);
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return ret;
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}
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EXPORT_SYMBOL_GPL(kvm_lapic_reg_write);
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@ -2160,7 +2182,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
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static_key_slow_dec_deferred(&apic_hw_disabled);
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} else {
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static_key_slow_inc(&apic_hw_disabled.key);
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recalculate_apic_map(vcpu->kvm);
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vcpu->kvm->arch.apic_map_dirty = true;
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}
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}
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@ -2201,6 +2223,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
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if (!apic)
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return;
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vcpu->kvm->arch.apic_map_dirty = false;
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/* Stop the timer in case it's a reset to an active apic */
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hrtimer_cancel(&apic->lapic_timer.timer);
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@ -2252,6 +2275,8 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
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vcpu->arch.apic_arb_prio = 0;
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vcpu->arch.apic_attention = 0;
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kvm_recalculate_apic_map(vcpu->kvm);
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}
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/*
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@ -2473,17 +2498,18 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
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struct kvm_lapic *apic = vcpu->arch.apic;
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int r;
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kvm_lapic_set_base(vcpu, vcpu->arch.apic_base);
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/* set SPIV separately to get count of SW disabled APICs right */
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apic_set_spiv(apic, *((u32 *)(s->regs + APIC_SPIV)));
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r = kvm_apic_state_fixup(vcpu, s, true);
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if (r)
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if (r) {
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kvm_recalculate_apic_map(vcpu->kvm);
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return r;
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}
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memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s));
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recalculate_apic_map(vcpu->kvm);
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kvm_recalculate_apic_map(vcpu->kvm);
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kvm_apic_set_version(vcpu);
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apic_update_ppr(apic);
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@ -78,6 +78,7 @@ void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8);
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void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu);
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void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value);
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u64 kvm_lapic_get_base(struct kvm_vcpu *vcpu);
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void kvm_recalculate_apic_map(struct kvm *kvm);
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void kvm_apic_set_version(struct kvm_vcpu *vcpu);
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int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val);
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int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
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@ -350,6 +350,7 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
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}
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kvm_lapic_set_base(vcpu, msr_info->data);
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kvm_recalculate_apic_map(vcpu->kvm);
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return 0;
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}
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EXPORT_SYMBOL_GPL(kvm_set_apic_base);
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