[1/4] powerpc/perf: Add perf interface to expose vpa counters

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 2ef9a5f4e5d1..b9bcbf999bd9 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -688,6 +688,9 @@  int kmvhv_counters_tracepoint_regfunc(void);
 void kmvhv_counters_tracepoint_unregfunc(void);
 int kvmhv_get_l2_counters_status(void);
 void kvmhv_set_l2_counters_status(int cpu, bool status);
+u64 kvmhv_get_l1_to_l2_cs_time(void);
+u64 kvmhv_get_l2_to_l1_cs_time(void);
+u64 kvmhv_get_l2_runtime_agg(void);
 
 #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
 
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index ad8dc4ccdaab..bc45cf09debc 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4153,6 +4153,7 @@  void kvmhv_set_l2_counters_status(int cpu, bool status)
 	else
 		lppaca_of(cpu).l2_counters_enable = 0;
 }
+EXPORT_SYMBOL(kvmhv_set_l2_counters_status);
 
 int kmvhv_counters_tracepoint_regfunc(void)
 {
@@ -4192,6 +4193,24 @@  static void do_trace_nested_cs_time(struct kvm_vcpu *vcpu)
 	*l2_runtime_agg_ptr = l2_runtime_ns;
 }
 
+u64 kvmhv_get_l1_to_l2_cs_time(void)
+{
+	return tb_to_ns(be64_to_cpu(get_lppaca()->l1_to_l2_cs_tb));
+}
+EXPORT_SYMBOL(kvmhv_get_l1_to_l2_cs_time);
+
+u64 kvmhv_get_l2_to_l1_cs_time(void)
+{
+	return tb_to_ns(be64_to_cpu(get_lppaca()->l2_to_l1_cs_tb));
+}
+EXPORT_SYMBOL(kvmhv_get_l2_to_l1_cs_time);
+
+u64 kvmhv_get_l2_runtime_agg(void)
+{
+	return tb_to_ns(be64_to_cpu(get_lppaca()->l2_runtime_tb));
+}
+EXPORT_SYMBOL(kvmhv_get_l2_runtime_agg);
+
 #else
 int kvmhv_get_l2_counters_status(void)
 {
diff --git a/arch/powerpc/perf/Makefile b/arch/powerpc/perf/Makefile
index 4f53d0b97539..ac2cf58d62db 100644
--- a/arch/powerpc/perf/Makefile
+++ b/arch/powerpc/perf/Makefile
@@ -16,6 +16,8 @@  obj-$(CONFIG_FSL_EMB_PERF_EVENT_E500) += e500-pmu.o e6500-pmu.o
 
 obj-$(CONFIG_HV_PERF_CTRS) += hv-24x7.o hv-gpci.o hv-common.o
 
+obj-$(CONFIG_VPA_PMU) += vpa-pmu.o
+
 obj-$(CONFIG_PPC_8xx) += 8xx-pmu.o
 
 obj-$(CONFIG_PPC64)		+= $(obj64-y)
diff --git a/arch/powerpc/perf/vpa-pmu.c b/arch/powerpc/perf/vpa-pmu.c
new file mode 100644
index 000000000000..0382973aeb8e
--- /dev/null
+++ b/arch/powerpc/perf/vpa-pmu.c
@@ -0,0 +1,197 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Performance monitoring support for Virtual Processor Area(VPA) based counters
+ *
+ * Copyright (C) 2024 IBM Corporation
+ */
+#define pr_fmt(fmt) "vpa_pmu: " fmt
+
+#include <linux/module.h>
+#include <linux/perf_event.h>
+#include <asm/kvm_ppc.h>
+#include <asm/kvm_book3s_64.h>
+
+#define MODULE_VERS "1.0"
+#define MODULE_NAME "pseries_vpa_pmu"
+
+#define EVENT(_name, _code)     enum{_name = _code}
+
+#define VPA_PMU_EVENT_VAR(_id)  event_attr_##_id
+#define VPA_PMU_EVENT_PTR(_id)  (&event_attr_##_id.attr.attr)
+
+static ssize_t vpa_pmu_events_sysfs_show(struct device *dev,
+				 struct device_attribute *attr, char *page)
+{
+	struct perf_pmu_events_attr *pmu_attr;
+
+	pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);
+
+	return sprintf(page, "event=0x%02llx\n", pmu_attr->id);
+}
+
+#define VPA_PMU_EVENT_ATTR(_name, _id)				\
+	PMU_EVENT_ATTR(_name, VPA_PMU_EVENT_VAR(_id), _id,	\
+			vpa_pmu_events_sysfs_show)
+
+EVENT(L1_TO_L2_CS_LAT,	0x1);
+EVENT(L2_TO_L1_CS_LAT,	0x2);
+EVENT(L2_RUNTIME_AGG,	0x3);
+
+VPA_PMU_EVENT_ATTR(l1_to_l2_lat,  L1_TO_L2_CS_LAT);
+VPA_PMU_EVENT_ATTR(l2_to_l1_lat,  L2_TO_L1_CS_LAT);
+VPA_PMU_EVENT_ATTR(l2_runtime_agg, L2_RUNTIME_AGG);
+
+static struct attribute *vpa_pmu_events_attr[] = {
+	VPA_PMU_EVENT_PTR(L1_TO_L2_CS_LAT),
+	VPA_PMU_EVENT_PTR(L2_TO_L1_CS_LAT),
+	VPA_PMU_EVENT_PTR(L2_RUNTIME_AGG),
+	NULL
+};
+
+static const struct attribute_group vpa_pmu_events_group = {
+	.name = "events",
+	.attrs = vpa_pmu_events_attr,
+};
+
+PMU_FORMAT_ATTR(event, "config:0-31");
+static struct attribute *vpa_pmu_format_attr[] = {
+	&format_attr_event.attr,
+	NULL,
+};
+
+static struct attribute_group vpa_pmu_format_group = {
+	.name = "format",
+	.attrs = vpa_pmu_format_attr,
+};
+
+static const struct attribute_group *vpa_pmu_attr_groups[] = {
+	&vpa_pmu_events_group,
+	&vpa_pmu_format_group,
+	NULL
+};
+
+static int vpa_pmu_event_init(struct perf_event *event)
+{
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	/* it does not support event sampling mode */
+	if (is_sampling_event(event))
+		return -EOPNOTSUPP;
+
+	/* no branch sampling */
+	if (has_branch_stack(event))
+		return -EOPNOTSUPP;
+
+	/* Invalid event code */
+	if ((event->attr.config <= 0) && (event->attr.config > 3))
+		return -EINVAL;
+
+	return 0;
+}
+
+static unsigned long get_counter_data(struct perf_event *event)
+{
+	unsigned int config = event->attr.config;
+	u64 data;
+
+	switch (config) {
+	case L1_TO_L2_CS_LAT:
+		data = kvmhv_get_l1_to_l2_cs_time();
+		break;
+	case L2_TO_L1_CS_LAT:
+		data = kvmhv_get_l2_to_l1_cs_time();
+		break;
+	case L2_RUNTIME_AGG:
+		data = kvmhv_get_l2_runtime_agg();
+		break;
+	default:
+		data = 0;
+		break;
+	}
+
+	return data;
+}
+
+static int vpa_pmu_add(struct perf_event *event, int flags)
+{
+	u64 data;
+
+	kvmhv_set_l2_counters_status(
+			smp_processor_id(), true);
+
+	data = get_counter_data(event);
+	local64_set(&event->hw.prev_count, data);
+
+	return 0;
+}
+
+static void vpa_pmu_read(struct perf_event *event)
+{
+	u64 prev_data, new_data, final_data;
+
+	prev_data = local64_read(&event->hw.prev_count);
+	new_data = get_counter_data(event);
+	final_data = new_data - prev_data;
+
+	local64_add(final_data, &event->count);
+}
+
+static void vpa_pmu_del(struct perf_event *event, int flags)
+{
+	vpa_pmu_read(event);
+
+	/*
+	 * Disable vpa counter accumulation
+	 */
+	kvmhv_set_l2_counters_status(
+			smp_processor_id(), false);
+}
+
+static struct pmu vpa_pmu = {
+	.task_ctx_nr	= perf_sw_context,
+	.name		= "vpa_pmu",
+	.event_init	= vpa_pmu_event_init,
+	.add		= vpa_pmu_add,
+	.del		= vpa_pmu_del,
+	.read		= vpa_pmu_read,
+	.attr_groups	= vpa_pmu_attr_groups,
+	.capabilities	= PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_NO_INTERRUPT,
+};
+
+static int __init pseries_vpa_pmu_init(void)
+{
+
+	/*
+	 * List of current Linux on Power platforms and
+	 * this driver is supported only in PowerVM LPAR
+	 * (L1) platform.
+	 *
+	 *	Enabled    Linux on Power Platforms
+	 *      ----------------------------------------
+	 *        [X]      PowerVM LPAR (L1)
+	 *        [ ]      KVM Guest On PowerVM KoP(L2)
+	 *        [ ]      Baremetal(PowerNV)
+	 *        [ ]      KVM Guest On PowerNV
+	 */
+	if (!(firmware_has_feature(FW_FEATURE_LPAR) && !is_kvm_guest()))
+		return -ENODEV;
+
+	perf_pmu_register(&vpa_pmu, vpa_pmu.name, -1);
+	pr_info("Virtual Processor Area PMU registered.\n");
+
+	return 0;
+}
+
+static void __exit pseries_vpa_pmu_cleanup(void)
+{
+	perf_pmu_unregister(&vpa_pmu);
+	pr_info("Virtual Processor Area PMU unregistered.\n");
+}
+
+module_init(pseries_vpa_pmu_init);
+module_exit(pseries_vpa_pmu_cleanup);
+MODULE_DESCRIPTION("Perf Driver for pSeries VPA pmu counter");
+MODULE_AUTHOR("Kajol Jain <kjain@linux.ibm.com>");
+MODULE_AUTHOR("Madhavan Srinivasan <maddy@linux.ibm.com>");
+MODULE_LICENSE("GPL");
diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index afc0f6a61337..42fc66e97539 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -140,6 +140,20 @@  config HV_PERF_CTRS
 
 	  If unsure, select Y.
 
+config VPA_PMU
+	tristate "VPA PMU events"
+	depends on KVM_BOOK3S_64_HV && HV_PERF_CTRS
+	help
+	  Enable access to the VPA PMU counters via perf. This enables
+	  code that support measurement for KVM on PowerVM(KoP) feature.
+	  PAPR hypervisor has introduced three new counters in the VPA area
+	  of LPAR CPUs for KVM L2 guest observability. Two for context switches
+	  from host to guest and vice versa, and one counter for getting
+	  the total time spent inside the KVM guest. This config enables code
+	  that access these software counters via perf.
+
+	  If unsure, Select N.
+
 config IBMVIO
 	depends on PPC_PSERIES
 	bool