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Commit de737089 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm/arm64: Enable adaptative WFE trapping 



Trapping blocking WFE is extremely beneficial in situations where
the system is oversubscribed, as it allows another thread to run
while being blocked. In a non-oversubscribed environment, this is
the complete opposite, and trapping WFE is just unnecessary overhead.

Let's only enable WFE trapping if the CPU has more than a single task
to run (that is, more than just the vcpu thread).

Reviewed-by: default avatarChristoffer Dall <christoffer.dall@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent 0a72a5ab

arch/arm/include/asm/kvm_emulate.h

+10 −0
Original line number Diff line number Diff line
@@ -107,6 +107,16 @@ static inline unsigned long *vcpu_hcr(const struct kvm_vcpu *vcpu) 
	return (unsigned long *)&vcpu->arch.hcr;

}



static inline void vcpu_clear_wfe_traps(struct kvm_vcpu *vcpu)

{

	vcpu->arch.hcr &= ~HCR_TWE;

}



static inline void vcpu_set_wfe_traps(struct kvm_vcpu *vcpu)

{

	vcpu->arch.hcr |= HCR_TWE;

}



static inline bool vcpu_mode_is_32bit(const struct kvm_vcpu *vcpu)

{

	return 1;

arch/arm64/include/asm/kvm_emulate.h

+10 −0
Original line number Diff line number Diff line
@@ -83,6 +83,16 @@ static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu) 
	return (unsigned long *)&vcpu->arch.hcr_el2;

}



static inline void vcpu_clear_wfe_traps(struct kvm_vcpu *vcpu)

{

	vcpu->arch.hcr_el2 &= ~HCR_TWE;

}



static inline void vcpu_set_wfe_traps(struct kvm_vcpu *vcpu)

{

	vcpu->arch.hcr_el2 |= HCR_TWE;

}



static inline void vcpu_set_vsesr(struct kvm_vcpu *vcpu, u64 vsesr)

{

	vcpu->arch.vsesr_el2 = vsesr;

virt/kvm/arm/arm.c

+6 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include <linux/kvm.h>

#include <linux/kvm_irqfd.h>

#include <linux/irqbypass.h>

#include <linux/sched/stat.h>

#include <trace/events/kvm.h>

#include <kvm/arm_pmu.h>

#include <kvm/arm_psci.h>
@@ -380,6 +381,11 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
	kvm_timer_vcpu_load(vcpu);

	kvm_vcpu_load_sysregs(vcpu);

	kvm_arch_vcpu_load_fp(vcpu);



	if (single_task_running())

		vcpu_clear_wfe_traps(vcpu);

	else

		vcpu_set_wfe_traps(vcpu);

}



void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)