[PATCH 2/2] KVM: arm64: Document PMU filtering API

@@ -36,6 +36,34 @@ 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.
 
+1.3 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_FILTER
+Parameters: in kvm_device_attr.addr the address for a PMU event filter is a
+            pointer to a struct kvm_pmu_event_filter
+Returns: -ENODEV: PMUv3 not supported or GIC not initialized
+         -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
+                 configured as required prior to calling this attribute
+         -EBUSY: PMUv3 already initialized
+
+Request the installation of a PMU event filter describe as follows:
+
+struct kvm_pmu_event_filter {
+	__u16	base_event;
+	__u16	nevents;
+
+#define KVM_PMU_EVENT_ALLOW	0
+#define KVM_PMU_EVENT_DENY	1
+
+	__u8	action;
+	__u8	pad[3];
+};
+
+A filter range is defined as the range [base_event, base_event + nevents[,
+together with an action (KVM_PMU_EVENT_ALLOW or KVM_PMU_EVENT_DENY). The
+first registered range defines the global policy (global ALLOW if the first
+action is DENY, global DENY if the first action is ALLOW). Multiple ranges
+can be programmed, and but fit within the 16bit space defined by the ARMv8.1
+PMU architecture.
+
 
 2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
 Architectures: ARM,ARM64