KVM: use jump label to optimize checking for in kernel local apic presence

Usually all vcpus have local apic pointer initialized, so the check may
be completely skipped.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 7f77e96ac5e8d4701158e8f04e0dfdb45f3992cd..650379ba73afd1407f4b97840a0e193bd733396c 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -152,6 +152,13 @@ static inline int apic_enabled(struct kvm_lapic *apic)
        return apic_sw_enabled(apic) && apic_hw_enabled(apic);
 }
 
+static inline bool vcpu_has_lapic(struct kvm_vcpu *vcpu)
+{
+       if (static_key_false(&kvm_no_apic_vcpu))
+               return vcpu->arch.apic;
+       return true;
+}
+
 #define LVT_MASK       \
        (APIC_LVT_MASKED | APIC_SEND_PENDING | APIC_VECTOR_MASK)
 
@@ -204,7 +211,7 @@ void kvm_apic_set_version(struct kvm_vcpu *vcpu)
        struct kvm_cpuid_entry2 *feat;
        u32 v = APIC_VERSION;
 
-       if (!irqchip_in_kernel(vcpu->kvm))
+       if (!vcpu_has_lapic(vcpu))
                return;
 
        feat = kvm_find_cpuid_entry(apic->vcpu, 0x1, 0);
@@ -305,7 +312,6 @@ static inline void apic_clear_isr(int vec, struct kvm_lapic *apic)
 
 int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
 {
-       struct kvm_lapic *apic = vcpu->arch.apic;
        int highest_irr;
 
        /* This may race with setting of irr in __apic_accept_irq() and
@@ -313,9 +319,9 @@ int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
         * will cause vmexit immediately and the value will be recalculated
         * on the next vmentry.
         */
-       if (!apic)
+       if (!vcpu_has_lapic(vcpu))
                return 0;
-       highest_irr = apic_find_highest_irr(apic);
+       highest_irr = apic_find_highest_irr(vcpu->arch.apic);
 
        return highest_irr;
 }
@@ -1061,9 +1067,7 @@ static int apic_mmio_write(struct kvm_io_device *this,
 
 void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu)
 {
-       struct kvm_lapic *apic = vcpu->arch.apic;
-
-       if (apic)
+       if (vcpu_has_lapic(vcpu))
                apic_reg_write(vcpu->arch.apic, APIC_EOI, 0);
 }
 EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi);
@@ -1098,10 +1102,9 @@ void kvm_free_lapic(struct kvm_vcpu *vcpu)
 u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
-       if (!apic)
-               return 0;
 
-       if (apic_lvtt_oneshot(apic) || apic_lvtt_period(apic))
+       if (!vcpu_has_lapic(vcpu) || apic_lvtt_oneshot(apic) ||
+                       apic_lvtt_period(apic))
                return 0;
 
        return apic->lapic_timer.tscdeadline;
@@ -1110,10 +1113,9 @@ u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu)
 void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
-       if (!apic)
-               return;
 
-       if (apic_lvtt_oneshot(apic) || apic_lvtt_period(apic))
+       if (!vcpu_has_lapic(vcpu) || apic_lvtt_oneshot(apic) ||
+                       apic_lvtt_period(apic))
                return;
 
        hrtimer_cancel(&apic->lapic_timer.timer);
@@ -1125,20 +1127,21 @@ void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
 
-       if (!apic)
+       if (!vcpu_has_lapic(vcpu))
                return;
+
        apic_set_tpr(apic, ((cr8 & 0x0f) << 4)
                     | (apic_get_reg(apic, APIC_TASKPRI) & 4));
 }
 
 u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu)
 {
-       struct kvm_lapic *apic = vcpu->arch.apic;
        u64 tpr;
 
-       if (!apic)
+       if (!vcpu_has_lapic(vcpu))
                return 0;
-       tpr = (u64) apic_get_reg(apic, APIC_TASKPRI);
+
+       tpr = (u64) apic_get_reg(vcpu->arch.apic, APIC_TASKPRI);
 
        return (tpr & 0xf0) >> 4;
 }
@@ -1237,7 +1240,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
 
 bool kvm_apic_present(struct kvm_vcpu *vcpu)
 {
-       return vcpu->arch.apic && apic_hw_enabled(vcpu->arch.apic);
+       return vcpu_has_lapic(vcpu) && apic_hw_enabled(vcpu->arch.apic);
 }
 
 int kvm_lapic_enabled(struct kvm_vcpu *vcpu)
@@ -1258,10 +1261,11 @@ static bool lapic_is_periodic(struct kvm_lapic *apic)
 
 int apic_has_pending_timer(struct kvm_vcpu *vcpu)
 {
-       struct kvm_lapic *lapic = vcpu->arch.apic;
+       struct kvm_lapic *apic = vcpu->arch.apic;
 
-       if (lapic && apic_enabled(lapic) && apic_lvt_enabled(lapic, APIC_LVTT))
-               return atomic_read(&lapic->lapic_timer.pending);
+       if (vcpu_has_lapic(vcpu) && apic_enabled(apic) &&
+                       apic_lvt_enabled(apic, APIC_LVTT))
+               return atomic_read(&apic->lapic_timer.pending);
 
        return 0;
 }
@@ -1371,7 +1375,7 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
        struct kvm_lapic *apic = vcpu->arch.apic;
        int highest_irr;
 
-       if (!apic || !apic_enabled(apic))
+       if (!vcpu_has_lapic(vcpu) || !apic_enabled(apic))
                return -1;
 
        apic_update_ppr(apic);
@@ -1399,7 +1403,10 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
 
-       if (apic && atomic_read(&apic->lapic_timer.pending) > 0) {
+       if (!vcpu_has_lapic(vcpu))
+               return;
+
+       if (atomic_read(&apic->lapic_timer.pending) > 0) {
                if (kvm_apic_local_deliver(apic, APIC_LVTT))
                        atomic_dec(&apic->lapic_timer.pending);
        }
@@ -1439,13 +1446,12 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu)
 
 void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
 {
-       struct kvm_lapic *apic = vcpu->arch.apic;
        struct hrtimer *timer;
 
-       if (!apic)
+       if (!vcpu_has_lapic(vcpu))
                return;
 
-       timer = &apic->lapic_timer.timer;
+       timer = &vcpu->arch.apic->lapic_timer.timer;
        if (hrtimer_cancel(timer))
                hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
 }
@@ -1602,7 +1608,7 @@ int kvm_hv_vapic_msr_write(struct kvm_vcpu *vcpu, u32 reg, u64 data)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
 
-       if (!irqchip_in_kernel(vcpu->kvm))
+       if (!vcpu_has_lapic(vcpu))
                return 1;
 
        /* if this is ICR write vector before command */
@@ -1616,7 +1622,7 @@ int kvm_hv_vapic_msr_read(struct kvm_vcpu *vcpu, u32 reg, u64 *data)
        struct kvm_lapic *apic = vcpu->arch.apic;
        u32 low, high = 0;
 
-       if (!irqchip_in_kernel(vcpu->kvm))
+       if (!vcpu_has_lapic(vcpu))
                return 1;
 
        if (apic_reg_read(apic, reg, 4, &low))

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 29fa18d27e6e2d7ca9bb87f63b9064eccf47a71e..8ebf65c349eb36ecd36feeb778c7ae17aab10fd2 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6152,6 +6152,8 @@ bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
        return irqchip_in_kernel(vcpu->kvm) == (vcpu->arch.apic != NULL);
 }
 
+struct static_key kvm_no_apic_vcpu __read_mostly;
+
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
        struct page *page;
@@ -6184,7 +6186,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
                r = kvm_create_lapic(vcpu);
                if (r < 0)
                        goto fail_mmu_destroy;
-       }
+       } else
+               static_key_slow_inc(&kvm_no_apic_vcpu);
 
        vcpu->arch.mce_banks = kzalloc(KVM_MAX_MCE_BANKS * sizeof(u64) * 4,
                                       GFP_KERNEL);
@@ -6224,6 +6227,8 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
        kvm_mmu_destroy(vcpu);
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
        free_page((unsigned long)vcpu->arch.pio_data);
+       if (!irqchip_in_kernel(vcpu->kvm))
+               static_key_slow_dec(&kvm_no_apic_vcpu);
 }
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)

diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 3d1134ddb885622af79bdb0fefb589c8f7b4d5b6..2b5219c12ac8566c24a837ccff3f2fb14db1c7f8 100644 (file)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -124,4 +124,5 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
 
 extern u64 host_xcr0;
 
+extern struct static_key kvm_no_apic_vcpu;
 #endif