arm64: KVM: Add accessors to track guest/host only counters

In order to effeciently switch events_{guest,host} perf counters at
guest entry/exit we add bitfields to kvm_cpu_context for guest and host
events as well as accessors for updating them.

A function is also provided which allows the PMU driver to determine
if a counter should start counting when it is enabled. With exclude_host,
we may only start counting when entering the guest.

Signed-off-by: Andrew Murray <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>

arch/arm64/include/asm/kvm_host.h

@@ -233,8 +233,14 @@ struct kvm_cpu_context {
 	struct kvm_vcpu *__hyp_running_vcpu;
 };
 
+struct kvm_pmu_events {
+	u32 events_host;
+	u32 events_guest;
+};
+
 struct kvm_host_data {
 	struct kvm_cpu_context host_ctxt;
+	struct kvm_pmu_events pmu_events;
 };
 
 typedef struct kvm_host_data kvm_host_data_t;
@@ -572,11 +578,22 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
 
+static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
+{
+	return attr->exclude_host;
+}
+
 #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
 static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 {
 	return kvm_arch_vcpu_run_map_fp(vcpu);
 }
+
+void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr);
+void kvm_clr_pmu_events(u32 clr);
+#else
+static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
+static inline void kvm_clr_pmu_events(u32 clr) {}
 #endif
 
 static inline void kvm_arm_vhe_guest_enter(void)

arch/arm64/kvm/Makefile

@@ -17,7 +17,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
 kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
 kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o
-kvm-$(CONFIG_KVM_ARM_HOST) += vgic-sys-reg-v3.o fpsimd.o
+kvm-$(CONFIG_KVM_ARM_HOST) += vgic-sys-reg-v3.o fpsimd.o pmu.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/aarch32.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic.o

arch/arm64/kvm/pmu.c

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 Arm Limited
+ * Author: Andrew Murray <[email protected]>
+ */
+#include <linux/kvm_host.h>
+#include <linux/perf_event.h>
+
+/*
+ * Given the exclude_{host,guest} attributes, determine if we are going
+ * to need to switch counters at guest entry/exit.
+ */
+static bool kvm_pmu_switch_needed(struct perf_event_attr *attr)
+{
+	/* Only switch if attributes are different */
+	return (attr->exclude_host != attr->exclude_guest);
+}
+
+/*
+ * Add events to track that we may want to switch at guest entry/exit
+ * time.
+ */
+void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr)
+{
+	struct kvm_host_data *ctx = this_cpu_ptr(&kvm_host_data);
+
+	if (!kvm_pmu_switch_needed(attr))
+		return;
+
+	if (!attr->exclude_host)
+		ctx->pmu_events.events_host |= set;
+	if (!attr->exclude_guest)
+		ctx->pmu_events.events_guest |= set;
+}
+
+/*
+ * Stop tracking events
+ */
+void kvm_clr_pmu_events(u32 clr)
+{
+	struct kvm_host_data *ctx = this_cpu_ptr(&kvm_host_data);
+
+	ctx->pmu_events.events_host &= ~clr;
+	ctx->pmu_events.events_guest &= ~clr;
+}