linux-kernel - [PATCH 2/2] KVM: arm/arm64: vgic: no need to call spin_lock

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Date:   Fri,  3 Aug 2018 21:57:04 +0800
From:   Jia He <hejianet@...il.com>
To:     Christoffer Dall <christoffer.dall@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Eric Auger <eric.auger@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Jia He <hejianet@...il.com>,
        Andre Przywara <andre.przywara@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, Jia He <jia.he@...-semitech.com>
Subject: [PATCH 2/2] KVM: arm/arm64: vgic: no need to call spin_lock_irqsave/restore when irq is disabled

Because kvm_vgic_sync_hwstate currently is definitly in the context
which irq is disabled (local_irq_disable/enable). There is no need to
call spin_lock_irqsave/restore in vgic_fold_lr_state and vgic_prune_ap_list

This patch replace them with the spin_lock/unlock no irq version

Signed-off-by: Jia He <jia.he@...-semitech.com>
---
 virt/kvm/arm/vgic/vgic-v2.c |  7 ++++---
 virt/kvm/arm/vgic/vgic-v3.c |  7 ++++---
 virt/kvm/arm/vgic/vgic.c    | 13 +++++++------
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index a5f2e44..487f5f2 100644
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -62,7 +62,8 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
 	struct vgic_v2_cpu_if *cpuif = &vgic_cpu->vgic_v2;
 	int lr;
-	unsigned long flags;
+
+	DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());
 
 	cpuif->vgic_hcr &= ~GICH_HCR_UIE;
 
@@ -83,7 +84,7 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 
 		irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
 
-		spin_lock_irqsave(&irq->irq_lock, flags);
+		spin_lock(&irq->irq_lock);
 
 		/* Always preserve the active bit */
 		irq->active = !!(val & GICH_LR_ACTIVE_BIT);
@@ -126,7 +127,7 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 				vgic_irq_set_phys_active(irq, false);
 		}
 
-		spin_unlock_irqrestore(&irq->irq_lock, flags);
+		spin_unlock(&irq->irq_lock);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
 
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index cdce653..b66b513 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -46,7 +46,8 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 	struct vgic_v3_cpu_if *cpuif = &vgic_cpu->vgic_v3;
 	u32 model = vcpu->kvm->arch.vgic.vgic_model;
 	int lr;
-	unsigned long flags;
+
+	DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());
 
 	cpuif->vgic_hcr &= ~ICH_HCR_UIE;
 
@@ -75,7 +76,7 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 		if (!irq)	/* An LPI could have been unmapped. */
 			continue;
 
-		spin_lock_irqsave(&irq->irq_lock, flags);
+		spin_lock(&irq->irq_lock);
 
 		/* Always preserve the active bit */
 		irq->active = !!(val & ICH_LR_ACTIVE_BIT);
@@ -118,7 +119,7 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 				vgic_irq_set_phys_active(irq, false);
 		}
 
-		spin_unlock_irqrestore(&irq->irq_lock, flags);
+		spin_unlock(&irq->irq_lock);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
 
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index c22cea6..7cfdfbc 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -593,10 +593,11 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
 	struct vgic_irq *irq, *tmp;
-	unsigned long flags;
+
+	DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());
 
 retry:
-	spin_lock_irqsave(&vgic_cpu->ap_list_lock, flags);
+	spin_lock(&vgic_cpu->ap_list_lock);
 
 	list_for_each_entry_safe(irq, tmp, &vgic_cpu->ap_list_head, ap_list) {
 		struct kvm_vcpu *target_vcpu, *vcpuA, *vcpuB;
@@ -637,7 +638,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
 		/* This interrupt looks like it has to be migrated. */
 
 		spin_unlock(&irq->irq_lock);
-		spin_unlock_irqrestore(&vgic_cpu->ap_list_lock, flags);
+		spin_unlock(&vgic_cpu->ap_list_lock);
 
 		/*
 		 * Ensure locking order by always locking the smallest
@@ -651,7 +652,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
 			vcpuB = vcpu;
 		}
 
-		spin_lock_irqsave(&vcpuA->arch.vgic_cpu.ap_list_lock, flags);
+		spin_lock(&vcpuA->arch.vgic_cpu.ap_list_lock);
 		spin_lock_nested(&vcpuB->arch.vgic_cpu.ap_list_lock,
 				 SINGLE_DEPTH_NESTING);
 		spin_lock(&irq->irq_lock);
@@ -676,7 +677,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
 
 		spin_unlock(&irq->irq_lock);
 		spin_unlock(&vcpuB->arch.vgic_cpu.ap_list_lock);
-		spin_unlock_irqrestore(&vcpuA->arch.vgic_cpu.ap_list_lock, flags);
+		spin_unlock(&vcpuA->arch.vgic_cpu.ap_list_lock);
 
 		if (target_vcpu_needs_kick) {
 			kvm_make_request(KVM_REQ_IRQ_PENDING, target_vcpu);
@@ -686,7 +687,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
 		goto retry;
 	}
 
-	spin_unlock_irqrestore(&vgic_cpu->ap_list_lock, flags);
+	spin_unlock(&vgic_cpu->ap_list_lock);
 }
 
 static inline void vgic_fold_lr_state(struct kvm_vcpu *vcpu)
-- 
1.8.3.1