path: root/Documentation
diff options
authorChristoffer Dall <>2016-09-26 18:51:47 -0700
committerGreg Kroah-Hartman <>2016-10-16 18:03:39 +0200
commit46848795ad096ece83489bbc8f6c8f32f42b21e8 (patch)
tree2185470becbc13be2c8581466d7488ce1583931a /Documentation
parent92b23841fcf85e3fe85b7ee70418965b404d5754 (diff)
KVM: arm64: Require in-kernel irqchip for PMU support
commit 6fe407f2d18a4f94216263f91cb7d1f08fa5887c upstream. If userspace creates a PMU for the VCPU, but doesn't create an in-kernel irqchip, then we end up in a nasty path where we try to take an uninitialized spinlock, which can lead to all sorts of breakages. Luckily, QEMU always creates the VGIC before the PMU, so we can establish this as ABI and check for the VGIC in the PMU init stage. This can be relaxed at a later time if we want to support PMU with a userspace irqchip. Cc: Shannon Zhao <> Acked-by: Marc Zyngier <> Signed-off-by: Christoffer Dall <> Signed-off-by: Greg Kroah-Hartman <>
Diffstat (limited to 'Documentation')
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/virtual/kvm/devices/vcpu.txt b/Documentation/virtual/kvm/devices/vcpu.txt
index c04165868faf..02f50686c418 100644
--- a/Documentation/virtual/kvm/devices/vcpu.txt
+++ b/Documentation/virtual/kvm/devices/vcpu.txt
@@ -30,4 +30,6 @@ Returns: -ENODEV: PMUv3 not supported
-EBUSY: PMUv3 already initialized
-Request the initialization of the PMUv3.
+Request the initialization of the PMUv3. This must be done after creating the
+in-kernel irqchip. Creating a PMU with a userspace irqchip is currently not