KVM: arm64: Opportunistically turn off WFI trapping when using direct…

… LPI injection Just like we do for WFE trapping, it can be useful to turn off WFI trapping when the physical CPU is not oversubscribed (that is, the vcpu is the only runnable process on this CPU) *and* that we're using direct injection of interrupts. The conditions are reevaluated on each vcpu_load(), ensuring that we don't switch to this mode on a busy system. On a GICv4 system, this has the effect of reducing the generation of doorbell interrupts to zero when the right conditions are met, which is a huge improvement over the current situation (where the doorbells are screaming if the CPU ever hits a blocking WFI). Signed-off-by: Marc Zyngier <[email protected]> Reviewed-by: Zenghui Yu <[email protected]> Reviewed-by: Christoffer Dall <[email protected]> Link: https://lore.kernel.org/r/[email protected]
ashr · Nov 8, 2019 · ef2e78d · ef2e78d
1 parent 5bd90b0
commit ef2e78d
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Showing 3 changed files with 11 additions and 6 deletions.
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
@@ -95,12 +95,12 @@ 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)
+static inline void vcpu_clear_wfx_traps(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hcr &= ~HCR_TWE;
 }
 
-static inline void vcpu_set_wfe_traps(struct kvm_vcpu *vcpu)
+static inline void vcpu_set_wfx_traps(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hcr |= HCR_TWE;
 }

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
@@ -87,14 +87,19 @@ 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)
+static inline void vcpu_clear_wfx_traps(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hcr_el2 &= ~HCR_TWE;
+	if (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count))
+		vcpu->arch.hcr_el2 &= ~HCR_TWI;
+	else
+		vcpu->arch.hcr_el2 |= HCR_TWI;
 }
 
-static inline void vcpu_set_wfe_traps(struct kvm_vcpu *vcpu)
+static inline void vcpu_set_wfx_traps(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hcr_el2 |= HCR_TWE;
+	vcpu->arch.hcr_el2 |= HCR_TWI;
 }
 
 static inline void vcpu_ptrauth_enable(struct kvm_vcpu *vcpu)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
@@ -386,9 +386,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	kvm_vcpu_pmu_restore_guest(vcpu);
 
 	if (single_task_running())
-		vcpu_clear_wfe_traps(vcpu);
+		vcpu_clear_wfx_traps(vcpu);
 	else
-		vcpu_set_wfe_traps(vcpu);
+		vcpu_set_wfx_traps(vcpu);
 
 	vcpu_ptrauth_setup_lazy(vcpu);
 }