From 6fe407f2d18a4f94216263f91cb7d1f08fa5887c Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Mon, 26 Sep 2016 18:51:47 -0700 Subject: [PATCH] KVM: arm64: Require in-kernel irqchip for PMU support 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: stable@vger.kernel.org Cc: Shannon Zhao Acked-by: Marc Zyngier Signed-off-by: Christoffer Dall --- Documentation/virtual/kvm/devices/vcpu.txt | 4 +++- virt/kvm/arm/pmu.c | 8 ++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) 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 attribute -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 +supported. diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c index a027569facfa..6e9c40eea208 100644 --- a/virt/kvm/arm/pmu.c +++ b/virt/kvm/arm/pmu.c @@ -423,6 +423,14 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu) if (!kvm_arm_support_pmu_v3()) return -ENODEV; + /* + * We currently require an in-kernel VGIC to use the PMU emulation, + * because we do not support forwarding PMU overflow interrupts to + * userspace yet. + */ + if (!irqchip_in_kernel(vcpu->kvm) || !vgic_initialized(vcpu->kvm)) + return -ENODEV; + if (!test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features) || !kvm_arm_pmu_irq_initialized(vcpu)) return -ENXIO; -- 2.20.1