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Commit c5cc421b authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

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



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

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent a181dc14

arch/x86/kvm/lapic.c

+28 −1
Original line number Diff line number Diff line
@@ -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);

}

arch/x86/kvm/lapic.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/x86.c

+1 −0
Original line number Diff line number Diff line
@@ -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: