[PATCH 3.16.y-ckt 059/129] arm/arm64: KVM: vgic: Fix error code in kvm_vgic_create()

[Luis Henriques]

3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoffer Dall <christoffer.dall@xxxxxxxxxx>

commit 6b50f54064a02b77a7b990032b80234fee59bcd6 upstream.

If we detect another vCPU is running we just exit and return 0 as if we
succesfully created the VGIC, but the VGIC wouldn't actual be created.

This shouldn't break in-kernel behavior because the kernel will not
observe the failed the attempt to create the VGIC, but userspace could
be rightfully confused.

Cc: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 virt/kvm/arm/vgic.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 078e704940b3..7f59965d4164 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1611,7 +1611,7 @@ out:
 
 int kvm_vgic_create(struct kvm *kvm)
 {
-	int i, vcpu_lock_idx = -1, ret = 0;
+	int i, vcpu_lock_idx = -1, ret;
 	struct kvm_vcpu *vcpu;
 
 	mutex_lock(&kvm->lock);
@@ -1626,6 +1626,7 @@ int kvm_vgic_create(struct kvm *kvm)
 	 * 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;
@@ -1633,11 +1634,10 @@ int kvm_vgic_create(struct kvm *kvm)
 	}
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (vcpu->arch.has_run_once) {
-			ret = -EBUSY;
+		if (vcpu->arch.has_run_once)
 			goto out_unlock;
-		}
 	}
+	ret = 0;
 
 	spin_lock_init(&kvm->arch.vgic.lock);
 	kvm->arch.vgic.vctrl_base = vgic_vctrl_base;
--
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