[PATCH 07/37] KVM: arm/arm64: Enable adaptative WFE trapping
From: Marc Zyngier <hidden>
Date: 2018-08-13 14:57:25
Also in:
kvm, kvmarm
Subsystem:
arm port, arm64 port (aarch64 architecture), kernel virtual machine (kvm), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Russell King, Catalin Marinas, Will Deacon, Paolo Bonzini, Marc Zyngier, Oliver Upton, Linus Torvalds
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: Christoffer Dall <redacted> Signed-off-by: Marc Zyngier <redacted> --- arch/arm/include/asm/kvm_emulate.h | 10 ++++++++++ arch/arm64/include/asm/kvm_emulate.h | 10 ++++++++++ virt/kvm/arm/arm.c | 6 ++++++ 3 files changed, 26 insertions(+)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
index 6493bd479ddc..b50fe8380868 100644
--- a/arch/arm/include/asm/kvm_emulate.h
+++ b/arch/arm/include/asm/kvm_emulate.h@@ -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;
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index dd98fdf33d99..bfefdd9a72eb 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h@@ -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;
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 04e554cae3a2..8e66b89a3db2 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c@@ -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)
--
2.18.0