linux-kernel - [PATCH RFC v3 4/9] KVM: arm/arm64: use locking helpers in kvm_vgic

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Message-Id: <20170821203530.9266-5-rkrcmar@redhat.com>
Date:   Mon, 21 Aug 2017 22:35:25 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mips@...ux-mips.org, kvm-ppc@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Christoffer Dall <cdall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        James Hogan <james.hogan@...tec.com>,
        Paul Mackerras <paulus@...abs.org>,
        Alexander Graf <agraf@...e.com>
Subject: [PATCH RFC v3 4/9] KVM: arm/arm64: use locking helpers in kvm_vgic_create()

No new VCPUs can be created because we are holding the kvm->lock.
This means that if we successfuly lock all VCPUs, we'll be unlocking the
same set and there is no need to do extra bookkeeping.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 virt/kvm/arm/vgic/vgic-init.c       | 24 +++++++++---------------
 virt/kvm/arm/vgic/vgic-kvm-device.c |  6 +++++-
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 5801261f3add..feb766f74c34 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -119,7 +119,7 @@ void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu)
  */
 int kvm_vgic_create(struct kvm *kvm, u32 type)
 {
-	int i, vcpu_lock_idx = -1, ret;
+	int i, ret;
 	struct kvm_vcpu *vcpu;
 
 	if (irqchip_in_kernel(kvm))
@@ -140,18 +140,14 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
 	 * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
 	 * that no other VCPUs are run while we create the vgic.
 	 */
-	ret = -EBUSY;
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (!mutex_trylock(&vcpu->mutex))
-			goto out_unlock;
-		vcpu_lock_idx = i;
-	}
+	if (!lock_all_vcpus(kvm))
+		return -EBUSY;
 
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (vcpu->arch.has_run_once)
+	kvm_for_each_vcpu(i, vcpu, kvm)
+		if (vcpu->arch.has_run_once) {
+			ret = -EBUSY;
 			goto out_unlock;
-	}
-	ret = 0;
+		}
 
 	if (type == KVM_DEV_TYPE_ARM_VGIC_V2)
 		kvm->arch.max_vcpus = VGIC_V2_MAX_CPUS;
@@ -176,11 +172,9 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
 	kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF;
 	kvm->arch.vgic.vgic_redist_base = VGIC_ADDR_UNDEF;
 
+	ret = 0;
 out_unlock:
-	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
-		vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
-		mutex_unlock(&vcpu->mutex);
-	}
+	unlock_all_vcpus(kvm);
 	return ret;
 }
 
diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
index 10ae6f394b71..c5124737c7fc 100644
--- a/virt/kvm/arm/vgic/vgic-kvm-device.c
+++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
@@ -270,7 +270,11 @@ static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx)
 
 void unlock_all_vcpus(struct kvm *kvm)
 {
-	unlock_vcpus(kvm, atomic_read(&kvm->online_vcpus) - 1);
+	int i;
+	struct kvm_vcpu *tmp_vcpu;
+
+	kvm_for_each_vcpu(i, tmp_vcpu, kvm)
+		mutex_unlock(&tmp_vcpu->mutex);
 }
 
 /* Returns true if all vcpus were locked, false otherwise */
-- 
2.13.3