[PATCH v2 4/6] kvm powerpc/book3s-apiv2: Introduce kvm-hv specific PMU

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Introduce a new PMU named 'kvm-hv' to report Book3s kvm-hv specific
performance counters. This will expose KVM-HV specific performance
attributes to user-space via kernel's PMU infrastructure and would enable
users to monitor active kvm-hv based guests.

The patch creates necessary scaffolding to for the new PMU callbacks and
introduces two new exports kvmppc_{,un}register_pmu() that are called from
kvm-hv init and exit function to perform initialize and cleanup for the
'kvm-hv' PMU. The patch doesn't introduce any perf-events yet, which will
be introduced in later patches

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>

---
Changelog

v1->v2:
* Fixed an issue of kvm-hv not loading on baremetal kvm [Gautam]
---
 arch/powerpc/include/asm/kvm_book3s.h |  12 +++
 arch/powerpc/kvm/Makefile             |   6 ++
 arch/powerpc/kvm/book3s_hv.c          |   9 ++
 arch/powerpc/kvm/book3s_hv_pmu.c      | 133 ++++++++++++++++++++++++++
 4 files changed, 160 insertions(+)
 create mode 100644 arch/powerpc/kvm/book3s_hv_pmu.c

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index e1ff291ba891..cf91a1493159 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -334,6 +334,9 @@ static inline bool kvmhv_is_nestedv1(void)
 	return !static_branch_likely(&__kvmhv_is_nestedv2);
 }
 
+int kvmppc_register_pmu(void);
+void kvmppc_unregister_pmu(void);
+
 #else
 
 static inline bool kvmhv_is_nestedv2(void)
@@ -346,6 +349,15 @@ static inline bool kvmhv_is_nestedv1(void)
 	return false;
 }
 
+static int kvmppc_register_pmu(void)
+{
+	return 0;
+}
+
+static void kvmppc_unregister_pmu(void)
+{
+}
+
 #endif
 
 int __kvmhv_nestedv2_reload_ptregs(struct kvm_vcpu *vcpu, struct pt_regs *regs);
diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
index 4bd9d1230869..094c3916d9d0 100644
--- a/arch/powerpc/kvm/Makefile
+++ b/arch/powerpc/kvm/Makefile
@@ -92,6 +92,12 @@ kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HANDLER) += \
 	$(kvm-book3s_64-builtin-tm-objs-y) \
 	$(kvm-book3s_64-builtin-xics-objs-y)
 
+# enable kvm_hv perf events
+ifdef CONFIG_HAVE_PERF_EVENTS
+kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HANDLER) += \
+	book3s_hv_pmu.o
+endif
+
 obj-$(CONFIG_GUEST_STATE_BUFFER_TEST) += test-guest-state-buffer.o
 endif
 
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 25429905ae90..6365b8126574 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -6662,6 +6662,14 @@ static int kvmppc_book3s_init_hv(void)
 		return r;
 	}
 
+	r = kvmppc_register_pmu();
+	if (r == -EOPNOTSUPP) {
+		pr_info("KVM-HV: PMU not supported %d\n", r);
+	} else if (r) {
+		pr_err("KVM-HV: Unable to register PMUs %d\n", r);
+		goto err;
+	}
+
 	kvm_ops_hv.owner = THIS_MODULE;
 	kvmppc_hv_ops = &kvm_ops_hv;
 
@@ -6676,6 +6684,7 @@ static int kvmppc_book3s_init_hv(void)
 
 static void kvmppc_book3s_exit_hv(void)
 {
+	kvmppc_unregister_pmu();
 	kvmppc_uvmem_free();
 	kvmppc_free_host_rm_ops();
 	if (kvmppc_radix_possible())
diff --git a/arch/powerpc/kvm/book3s_hv_pmu.c b/arch/powerpc/kvm/book3s_hv_pmu.c
new file mode 100644
index 000000000000..8c6ed30b7654
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_hv_pmu.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Description: PMUs specific to running nested KVM-HV guests
+ * on Book3S processors (specifically POWER9 and later).
+ */
+
+#define pr_fmt(fmt)  "kvmppc-pmu: " fmt
+
+#include "asm-generic/local64.h"
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/ratelimit.h>
+#include <linux/kvm_host.h>
+#include <linux/gfp_types.h>
+#include <linux/pgtable.h>
+#include <linux/perf_event.h>
+#include <linux/spinlock_types.h>
+#include <linux/spinlock.h>
+
+#include <asm/types.h>
+#include <asm/kvm_ppc.h>
+#include <asm/kvm_book3s.h>
+#include <asm/mmu.h>
+#include <asm/pgalloc.h>
+#include <asm/pte-walk.h>
+#include <asm/reg.h>
+#include <asm/plpar_wrappers.h>
+#include <asm/firmware.h>
+
+enum kvmppc_pmu_eventid {
+	KVMPPC_EVENT_MAX,
+};
+
+static struct attribute *kvmppc_pmu_events_attr[] = {
+	NULL,
+};
+
+static const struct attribute_group kvmppc_pmu_events_group = {
+	.name = "events",
+	.attrs = kvmppc_pmu_events_attr,
+};
+
+PMU_FORMAT_ATTR(event, "config:0");
+static struct attribute *kvmppc_pmu_format_attr[] = {
+	&format_attr_event.attr,
+	NULL,
+};
+
+static struct attribute_group kvmppc_pmu_format_group = {
+	.name = "format",
+	.attrs = kvmppc_pmu_format_attr,
+};
+
+static const struct attribute_group *kvmppc_pmu_attr_groups[] = {
+	&kvmppc_pmu_events_group,
+	&kvmppc_pmu_format_group,
+	NULL,
+};
+
+static int kvmppc_pmu_event_init(struct perf_event *event)
+{
+	unsigned int config = event->attr.config;
+
+	pr_debug("%s: Event(%p) id=%llu cpu=%x on_cpu=%x config=%u",
+		 __func__, event, event->id, event->cpu,
+		 event->oncpu, config);
+
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	if (config >= KVMPPC_EVENT_MAX)
+		return -EINVAL;
+
+	local64_set(&event->hw.prev_count, 0);
+	local64_set(&event->count, 0);
+
+	return 0;
+}
+
+static void kvmppc_pmu_del(struct perf_event *event, int flags)
+{
+}
+
+static int kvmppc_pmu_add(struct perf_event *event, int flags)
+{
+	return 0;
+}
+
+static void kvmppc_pmu_read(struct perf_event *event)
+{
+}
+
+/* L1 wide counters PMU */
+static struct pmu kvmppc_pmu = {
+	.task_ctx_nr = perf_sw_context,
+	.name = "kvm-hv",
+	.event_init = kvmppc_pmu_event_init,
+	.add = kvmppc_pmu_add,
+	.del = kvmppc_pmu_del,
+	.read = kvmppc_pmu_read,
+	.attr_groups = kvmppc_pmu_attr_groups,
+	.type = -1,
+};
+
+int kvmppc_register_pmu(void)
+{
+	int rc = -EOPNOTSUPP;
+
+	/* only support events for nestedv2 right now */
+	if (kvmhv_is_nestedv2()) {
+		/* Setup done now register the PMU */
+		pr_info("Registering kvm-hv pmu");
+
+		/* Register only if we arent already registered */
+		rc = (kvmppc_pmu.type == -1) ?
+			     perf_pmu_register(&kvmppc_pmu, kvmppc_pmu.name,
+					       -1) : 0;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(kvmppc_register_pmu);
+
+void kvmppc_unregister_pmu(void)
+{
+	if (kvmhv_is_nestedv2()) {
+		if (kvmppc_pmu.type != -1)
+			perf_pmu_unregister(&kvmppc_pmu);
+
+		pr_info("kvmhv_pmu unregistered.\n");
+	}
+}
+EXPORT_SYMBOL_GPL(kvmppc_unregister_pmu);
-- 
2.47.1