[PATCH v7 06/12] KVM: arm64: PMU: Add a helper to read the number of counters

[Raghavendra Rao Ananta <rananta@google.com>]

Add a helper, kvm_arm_get_num_counters(), to read the number
of counters from the arm_pmu associated to the VM. Make the
function global as upcoming patches will be interested to
know the value while setting the PMCR.N of the guest from
userspace.

Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
---
 arch/arm64/kvm/pmu-emul.c | 17 +++++++++++++++++
 include/kvm/arm_pmu.h     |  6 ++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index a161d6266a5c..84aa8efd9163 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -873,6 +873,23 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
 	return true;
 }
 
+/**
+ * kvm_arm_get_num_counters - Get the number of general-purpose PMU counters.
+ * @kvm: The kvm pointer
+ */
+int kvm_arm_get_num_counters(struct kvm *kvm)
+{
+	struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
+
+	lockdep_assert_held(&kvm->arch.config_lock);
+
+	/*
+	 * The arm_pmu->num_events considers the cycle counter as well.
+	 * Ignore that and return only the general-purpose counters.
+	 */
+	return arm_pmu->num_events - 1;
+}
+
 static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
 {
 	lockdep_assert_held(&kvm->arch.config_lock);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index cd980d78b86b..672f3e9d7eea 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -102,6 +102,7 @@ void kvm_vcpu_pmu_resync_el0(void);
 
 u8 kvm_arm_pmu_get_pmuver_limit(void);
 int kvm_arm_set_default_pmu(struct kvm *kvm);
+int kvm_arm_get_num_counters(struct kvm *kvm);
 
 u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu);
 #else
@@ -181,6 +182,11 @@ static inline int kvm_arm_set_default_pmu(struct kvm *kvm)
 	return -ENODEV;
 }
 
+static inline int kvm_arm_get_num_counters(struct kvm *kvm)
+{
+	return -ENODEV;
+}
+
 static inline u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
 {
 	return 0;
-- 
2.42.0.609.gbb76f46606-goog