The resctrl file system passes requests to read event monitor files to
the architecture resctrl_arch_rmid_read() to collect values
from hardware counters.

Use the resctrl resource to differentiate between calls to read legacy
L3 events from the new telemetry events (which are attached to
RDT_RESOURCE_PERF_PKG).

There may be multiple aggregators tracking each package, so scan all of
them and add up all counters.

Enable the events marked as readable from any CPU providing an
mon_evt::arch_priv pointer to the struct pmt_event for each
event.

At run time when a user reads an event file the file system code
provides the enum resctrl_event_id for the event and the arch_priv
pointer that was supplied when the event was enabled.

Resctrl now uses readq() so depends on X86_64. Update Kconfig.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/resctrl/internal.h  |  7 ++++
 arch/x86/kernel/cpu/resctrl/intel_aet.c | 46 +++++++++++++++++++++++++
 arch/x86/kernel/cpu/resctrl/monitor.c   |  3 ++
 arch/x86/Kconfig                        |  2 +-
 4 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 36a2072c19c7..0081fb5a4420 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -172,9 +172,16 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 #ifdef CONFIG_X86_RESCTRL_CPU_INTEL_AET
 bool intel_aet_get_events(void);
 void __exit intel_aet_exit(void);
+int intel_aet_read_event(int domid, int rmid, enum resctrl_event_id evtid,
+			 void *arch_priv, u64 *val);
 #else
 static inline bool intel_aet_get_events(void) { return false; }
 static inline void __exit intel_aet_exit(void) { }
+static inline int intel_aet_read_event(int domid, int rmid, enum resctrl_event_id evtid,
+				       void *arch_priv, u64 *val)
+{
+	return -EINVAL;
+}
 #endif
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index f4bf0f2ccf26..bd6011a95d12 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -14,6 +14,7 @@
 #include <linux/cleanup.h>
 #include <linux/cpu.h>
 #include <linux/intel_vsec.h>
+#include <linux/io.h>
 #include <linux/resctrl.h>
 #include <linux/slab.h>
 
@@ -213,6 +214,13 @@ static int discover_events(struct event_group *e, struct pmt_feature_group *p)
 
 	list_add(&e->list, &active_event_groups);
 
+	for (int i = 0; i < e->num_events; i++) {
+		enum resctrl_event_id eventid;
+
+		eventid = e->evts[i].id;
+		resctrl_enable_mon_event(eventid, true, e->evts[i].bin_bits, &e->evts[i]);
+	}
+
 	return 0;
 }
 
@@ -279,3 +287,41 @@ void __exit intel_aet_exit(void)
 		list_del(&evg->list);
 	}
 }
+
+#define DATA_VALID	BIT_ULL(63)
+#define DATA_BITS	GENMASK_ULL(62, 0)
+
+/*
+ * Read counter for an event on a domain (summing all aggregators
+ * on the domain).
+ */
+int intel_aet_read_event(int domid, int rmid, enum resctrl_event_id eventid,
+			 void *arch_priv, u64 *val)
+{
+	struct pmt_event *pevt = arch_priv;
+	struct pkg_mmio_info *mmi;
+	struct event_group *e;
+	u64 evtcount;
+	void *pevt0;
+	int idx;
+
+	pevt0 = pevt - pevt->idx;
+	e = container_of(pevt0, struct event_group, evts);
+	idx = rmid * e->num_events;
+	idx += pevt->idx;
+	mmi = e->pkginfo[domid];
+
+	if (idx * sizeof(u64) + sizeof(u64) > e->mmio_size) {
+		pr_warn_once("MMIO index %d out of range\n", idx);
+		return -EIO;
+	}
+
+	for (int i = 0; i < mmi->num_regions; i++) {
+		evtcount = readq(mmi->addrs[i] + idx * sizeof(u64));
+		if (!(evtcount & DATA_VALID))
+			return -EINVAL;
+		*val += evtcount & DATA_BITS;
+	}
+
+	return 0;
+}
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 185b203f6321..51d7d99336c6 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -232,6 +232,9 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain_hdr *hdr,
 
 	resctrl_arch_rmid_read_context_check();
 
+	if (r->rid == RDT_RESOURCE_PERF_PKG)
+		return intel_aet_read_event(hdr->id, rmid, eventid, arch_priv, val);
+
 	if (r->rid != RDT_RESOURCE_L3)
 		return -EINVAL;
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 21c2d1022b15..512286ef6d71 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -530,7 +530,7 @@ config X86_CPU_RESCTRL
 
 config X86_RESCTRL_CPU_INTEL_AET
 	bool "Intel Application Energy Telemetry" if INTEL_PMT_DISCOVERY=y
-	depends on X86_CPU_RESCTRL && CPU_SUP_INTEL
+	depends on X86_64 && X86_CPU_RESCTRL && CPU_SUP_INTEL
 	help
 	  Enable per-RMID telemetry events in resctrl
 
-- 
2.50.0

Hi Tony,

On 7/11/25 4:53 PM, Tony Luck wrote:
> The resctrl file system passes requests to read event monitor files to
> the architecture resctrl_arch_rmid_read() to collect values
> from hardware counters.
> 
> Use the resctrl resource to differentiate between calls to read legacy
> L3 events from the new telemetry events (which are attached to
> RDT_RESOURCE_PERF_PKG).
> 
> There may be multiple aggregators tracking each package, so scan all of
> them and add up all counters.
> 
> Enable the events marked as readable from any CPU providing an
> mon_evt::arch_priv pointer to the struct pmt_event for each
> event.
> 
> At run time when a user reads an event file the file system code
> provides the enum resctrl_event_id for the event and the arch_priv
> pointer that was supplied when the event was enabled.

The changelog ordering seems random. It starts by describing how reading of events are
handled and how counters are added when an event is read, then describes enabling the
events (this should happen before an event can be read?), then how data is passed when
reading an event (that should be followed by adding up the counters?).

I think it may help to clearly describe the phases involved. For example, start
with how events are enabled during enumeration/discovery, then how data is
passed during runtime when a user reads an event file, then how the
data is collected.

> 
> Resctrl now uses readq() so depends on X86_64. Update Kconfig.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
...

> diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> index f4bf0f2ccf26..bd6011a95d12 100644
> --- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
> +++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> @@ -14,6 +14,7 @@
>  #include <linux/cleanup.h>
>  #include <linux/cpu.h>
>  #include <linux/intel_vsec.h>
> +#include <linux/io.h>
>  #include <linux/resctrl.h>
>  #include <linux/slab.h>
>  
> @@ -213,6 +214,13 @@ static int discover_events(struct event_group *e, struct pmt_feature_group *p)
>  
>  	list_add(&e->list, &active_event_groups);
>  

Should this addition be documented as "step 3"?

> +	for (int i = 0; i < e->num_events; i++) {
> +		enum resctrl_event_id eventid;
> +
> +		eventid = e->evts[i].id;
> +		resctrl_enable_mon_event(eventid, true, e->evts[i].bin_bits, &e->evts[i]);

Why is eventid needed? I think using e->evts[i].id makes it more obvious how
the parameters relate.

> +	}
> +
>  	return 0;
>  }
>  

Reinette