[PATCH v3 14/26] x86/resctrl: Add first part of telemetry event enumeration

[Tony Luck <tony.luck@intel.com>]

The OOBMSM driver provides an interface to discover any RMID
based events for "energy" and "perf" classes.

Hold onto references to any pmt_feature_groups that resctrl
uses until resctrl exit.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/resctrl/internal.h  |  8 ++++
 arch/x86/kernel/cpu/resctrl/core.c      |  5 ++
 arch/x86/kernel/cpu/resctrl/intel_aet.c | 62 +++++++++++++++++++++++++
 arch/x86/kernel/cpu/resctrl/Makefile    |  1 +
 4 files changed, 76 insertions(+)
 create mode 100644 arch/x86/kernel/cpu/resctrl/intel_aet.c

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 45eabc7919c6..70b63bbc429d 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -172,4 +172,12 @@ void __init intel_rdt_mbm_apply_quirk(void);
 
 void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 
+#ifdef CONFIG_INTEL_AET_RESCTRL
+bool intel_aet_get_events(void);
+void __exit intel_aet_exit(void);
+#else
+static inline bool intel_aet_get_events(void) { return false; }
+static inline void intel_aet_exit(void) { };
+#endif
+
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index a066a9c54a1f..f0f256a5ac66 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -718,6 +718,9 @@ void resctrl_arch_mount(void)
 	if (only_once)
 		return;
 	only_once = true;
+
+	if (!intel_aet_get_events())
+		return;
 }
 
 enum {
@@ -1063,6 +1066,8 @@ late_initcall(resctrl_arch_late_init);
 
 static void __exit resctrl_arch_exit(void)
 {
+	intel_aet_exit();
+
 	cpuhp_remove_state(rdt_online);
 
 	resctrl_exit();
diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
new file mode 100644
index 000000000000..8e531ad279b5
--- /dev/null
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Resource Director Technology(RDT)
+ * - Intel Application Energy Telemetry
+ *
+ * Copyright (C) 2025 Intel Corporation
+ *
+ * Author:
+ *    Tony Luck <tony.luck@intel.com>
+ */
+
+#define pr_fmt(fmt)   "resctrl: " fmt
+
+#include <linux/cpu.h>
+#include <linux/cleanup.h>
+#include "fake_intel_aet_features.h"
+#include <linux/intel_vsec.h>
+#include <linux/resctrl.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static struct pmt_feature_group *feat_energy;
+static struct pmt_feature_group *feat_perf;
+
+DEFINE_FREE(intel_pmt_put_feature_group, struct pmt_feature_group *,	\
+	if (!IS_ERR_OR_NULL(_T))					\
+		intel_pmt_put_feature_group(_T))
+
+/*
+ * Ask OOBMSM discovery driver for all the RMID based telemetry groups
+ * that it supports.
+ */
+bool intel_aet_get_events(void)
+{
+	struct pmt_feature_group *p1 __free(intel_pmt_put_feature_group) = NULL;
+	struct pmt_feature_group *p2 __free(intel_pmt_put_feature_group) = NULL;
+	bool use_p1, use_p2;
+
+	p1 = intel_pmt_get_regions_by_feature(FEATURE_PER_RMID_ENERGY_TELEM);
+	p2 = intel_pmt_get_regions_by_feature(FEATURE_PER_RMID_PERF_TELEM);
+	use_p1 = !IS_ERR_OR_NULL(p1);
+	use_p2 = !IS_ERR_OR_NULL(p2);
+
+	if (!use_p1 && !use_p2)
+		return false;
+
+	if (use_p1)
+		feat_energy = no_free_ptr(p1);
+	if (use_p2)
+		feat_perf = no_free_ptr(p2);
+
+	return true;
+}
+
+void __exit intel_aet_exit(void)
+{
+	if (feat_energy)
+		intel_pmt_put_feature_group(feat_energy);
+	if (feat_perf)
+		intel_pmt_put_feature_group(feat_perf);
+}
diff --git a/arch/x86/kernel/cpu/resctrl/Makefile b/arch/x86/kernel/cpu/resctrl/Makefile
index c56d3acf8ac7..74c3b2333dde 100644
--- a/arch/x86/kernel/cpu/resctrl/Makefile
+++ b/arch/x86/kernel/cpu/resctrl/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_X86_CPU_RESCTRL)		+= core.o rdtgroup.o monitor.o
 obj-$(CONFIG_X86_CPU_RESCTRL)		+= ctrlmondata.o
+obj-$(CONFIG_INTEL_AET_RESCTRL)		+= intel_aet.o
 obj-$(CONFIG_INTEL_AET_RESCTRL)		+= fake_intel_aet_features.o
 obj-$(CONFIG_RESCTRL_FS_PSEUDO_LOCK)	+= pseudo_lock.o
 
-- 
2.48.1