KVM: arm/arm64: Fix GICv4 ITS initialization issues

We should only try to initialize GICv4 data structures on a GICv4
capable system.  Move the vgic_supports_direct_msis() check inito
vgic_v4_init() so that any KVM VGIC initialization path does not fail
on non-GICv4 systems.

Also be slightly more strict in the checking of the return value in
vgic_its_create, and only error out on negative return values from the
vgic_v4_init() function.  This is important because the kvm device code
only treats negative values as errors and only cleans up in this case.
Errornously treating a positive return value as an error from the
vgic_v4_init() function can lead to NULL pointer dereferences, as has
recently been observed.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index b8c1b724ba3e..c93ecd4a903b 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1673,7 +1673,7 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
 
 	if (vgic_initialized(dev->kvm)) {
 		int ret = vgic_v4_init(dev->kvm);
-		if (ret) {
+		if (ret < 0) {
 			kfree(its);
 			return ret;
 		}