[PATCH 1/5] KVM: arm64: Allow creating the PMU without the in-kernel GIC

[Christoffer Dall]

Since we got support for devices in userspace which allows reporting the
PMU overflow output status to userspace, we should actually allow
creating the PMU on systems without an in-kernel irqchip, which in turn
requires us to slightly clarify error codes for the ABI and move things
around for the initialization phase.

Signed-off-by: Christoffer Dall <cdall at linaro.org>
---
 Documentation/virtual/kvm/devices/vcpu.txt | 16 +++++++++-------
 virt/kvm/arm/pmu.c                         | 27 +++++++++++++++++----------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/Documentation/virtual/kvm/devices/vcpu.txt b/Documentation/virtual/kvm/devices/vcpu.txt
index 02f5068..352af6e 100644
--- a/Documentation/virtual/kvm/devices/vcpu.txt
+++ b/Documentation/virtual/kvm/devices/vcpu.txt
@@ -16,7 +16,9 @@ Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt is a
 Returns: -EBUSY: The PMU overflow interrupt is already set
          -ENXIO: The overflow interrupt not set when attempting to get it
          -ENODEV: PMUv3 not supported
-         -EINVAL: Invalid PMU overflow interrupt number supplied
+         -EINVAL: Invalid PMU overflow interrupt number supplied or
+                  trying to set the IRQ number without using an in-kernel
+                  irqchip.
 
 A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
 number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
@@ -25,11 +27,11 @@ all vcpus, while as an SPI it must be a separate number per vcpu.
 
 1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
 Parameters: no additional parameter in kvm_device_attr.addr
-Returns: -ENODEV: PMUv3 not supported
-         -ENXIO: PMUv3 not properly configured as required prior to calling this
-                 attribute
+Returns: -ENODEV: PMUv3 not supported or GIC not initialized
+         -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
+                 conigured as required prior to calling this attribute
          -EBUSY: PMUv3 already initialized
 
-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.
+Request the initialization of the PMUv3.  If using the PMUv3 with an in-kernel
+virtual GIC implementation, this must be done after initializing the in-kernel
+irqchip.
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 4b43e7f..f046b08 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -456,21 +456,25 @@ 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))
+	if (!test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
 		return -ENXIO;
 
 	if (kvm_arm_pmu_v3_ready(vcpu))
 		return -EBUSY;
 
+	if (irqchip_in_kernel(vcpu->kvm)) {
+		/*
+		 * If using the PMU with an in-kernel virtual GIC
+		 * implementation, we require the GIC to be already
+		 * initialized when initializing the PMU.
+		 */
+		if (!vgic_initialized(vcpu->kvm))
+			return -ENODEV;
+
+		if (!kvm_arm_pmu_irq_initialized(vcpu))
+			return -ENXIO;
+	}
+
 	kvm_pmu_vcpu_reset(vcpu);
 	vcpu->arch.pmu.ready = true;
 
@@ -512,6 +516,9 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 		int __user *uaddr = (int __user *)(long)attr->addr;
 		int irq;
 
+		if (!irqchip_in_kernel(vcpu->kvm))
+			return -EINVAL;
+
 		if (!test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
 			return -ENODEV;
 
-- 
2.9.0