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KVM: use jump label to optimize checking for HW enabled APIC in APIC_BASE MSR

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Usually all APICs are HW enabled so the check can be optimized out.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Gleb Natapov 2012-08-05 15:58:30 +03:00 • committed by Avi Kivity
parent a181dc14ed
commit c5cc421ba3
3 changed files with 30 additions and 1 deletions
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29
arch/x86/kvm/lapic.c
View file

@ -34,6 +34,7 @@
#include <asm/current.h>
#include <asm/apicdef.h>
#include <linux/atomic.h>
#include <linux/jump_label.h>
#include "kvm_cache_regs.h"
#include "irq.h"
#include "trace.h"
@ -117,9 +118,13 @@ static inline int __apic_test_and_clear_vector(int vec, void *bitmap)
return __test_and_clear_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
}
struct static_key_deferred apic_hw_disabled __read_mostly;
static inline int apic_hw_enabled(struct kvm_lapic *apic)
{
return (apic)->vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE;
if (static_key_false(&apic_hw_disabled.key))
return apic->vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE;
return MSR_IA32_APICBASE_ENABLE;
}
static inline int apic_sw_enabled(struct kvm_lapic *apic)
@ -1055,6 +1060,9 @@ void kvm_free_lapic(struct kvm_vcpu *vcpu)
hrtimer_cancel(&vcpu->arch.apic->lapic_timer.timer);
if (!(vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE))
static_key_slow_dec_deferred(&apic_hw_disabled);
if (vcpu->arch.apic->regs)
free_page((unsigned long)vcpu->arch.apic->regs);
@ -1125,6 +1133,14 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
return;
}
/* update jump label if enable bit changes */
if ((vcpu->arch.apic_base ^ value) & MSR_IA32_APICBASE_ENABLE) {
if (value & MSR_IA32_APICBASE_ENABLE)
static_key_slow_dec_deferred(&apic_hw_disabled);
else
static_key_slow_inc(&apic_hw_disabled.key);
}
if (!kvm_vcpu_is_bsp(apic->vcpu))
value &= ~MSR_IA32_APICBASE_BSP;
@ -1311,6 +1327,11 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
HRTIMER_MODE_ABS);
apic->lapic_timer.timer.function = apic_timer_fn;
/*
* APIC is created enabled. This will prevent kvm_lapic_set_base from
* thinking that APIC satet has changed.
*/
vcpu->arch.apic_base = MSR_IA32_APICBASE_ENABLE;
kvm_lapic_set_base(vcpu,
APIC_DEFAULT_PHYS_BASE | MSR_IA32_APICBASE_ENABLE);
@ -1598,3 +1619,9 @@ int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data)
return kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.pv_eoi.data,
addr);
}
void kvm_lapic_init(void)
{
/* do not patch jump label more than once per second */
jump_label_rate_limit(&apic_hw_disabled, HZ);
}

1
arch/x86/kvm/lapic.h
View file

@ -78,4 +78,5 @@ static inline bool kvm_hv_vapic_assist_page_enabled(struct kvm_vcpu *vcpu)
}
int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data);
void kvm_lapic_init(void);
#endif

1
arch/x86/kvm/x86.c
View file

@ -4903,6 +4903,7 @@ int kvm_arch_init(void *opaque)
if (cpu_has_xsave)
host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
kvm_lapic_init();
return 0;
out: