[3.16.y-ckt stable] Patch "arm/arm64: KVM: vgic: Fix error code in kvm_vgic_create()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    arm/arm64: KVM: vgic: Fix error code in kvm_vgic_create()

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 1cc87e5548572e4060fd1e7041517d7d0c5aeae0 Mon Sep 17 00:00:00 2001
From: Christoffer Dall <christoffer.dall at linaro.org>
Date: Thu, 6 Nov 2014 11:47:39 +0000
Subject: arm/arm64: KVM: vgic: Fix error code in kvm_vgic_create()

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 at arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Shannon Zhao <shannon.zhao at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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;