linux-kernel - [PATCH v13 29/32] x86/resctrl: Enable RDT_RESOURCE_PERF

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Message-ID: <20251029162118.40604-30-tony.luck@intel.com>
Date: Wed, 29 Oct 2025 09:21:12 -0700
From: Tony Luck <tony.luck@...el.com>
To: Fenghua Yu <fenghuay@...dia.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	James Morse <james.morse@....com>,
	Babu Moger <babu.moger@....com>,
	Drew Fustini <dfustini@...libre.com>,
	Dave Martin <Dave.Martin@....com>,
	Chen Yu <yu.c.chen@...el.com>
Cc: x86@...nel.org,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev,
	Tony Luck <tony.luck@...el.com>
Subject: [PATCH v13 29/32] x86/resctrl: Enable RDT_RESOURCE_PERF_PKG

Since telemetry events are enumerated on resctrl mount the RDT_RESOURCE_PERF_PKG
resource is not considered "monitoring capable" during early resctrl initialization.
This means that the domain list for RDT_RESOURCE_PERF_PKG is not built when the CPU
hot plug notifiers are registered and run for the first time right after resctrl
initialization.

Mark the RDT_RESOURCE_PERF_PKG as "monitoring capable" upon successful telemetry
event enumeration to ensure future CPU hotplug events include this resource and
initialize its domain list for CPUs that are already online.

Print to console log announcing the name of the telemetry feature detected.

Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/resctrl/core.c      | 16 +++++++++++++++-
 arch/x86/kernel/cpu/resctrl/intel_aet.c |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 9eb1bca9436b..7a9c7e6ad712 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -761,14 +761,28 @@ static int resctrl_arch_offline_cpu(unsigned int cpu)
 
 void resctrl_arch_pre_mount(void)
 {
+	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl;
 	static atomic_t only_once = ATOMIC_INIT(0);
-	int old = 0;
+	int cpu, old = 0;
 
 	if (!atomic_try_cmpxchg(&only_once, &old, 1))
 		return;
 
 	if (!intel_aet_get_events())
 		return;
+
+	/*
+	 * Late discovery of telemetry events means the domains for the
+	 * resource were not built. Do that now.
+	 */
+	cpus_read_lock();
+	mutex_lock(&domain_list_lock);
+	r->mon_capable = true;
+	rdt_mon_capable = true;
+	for_each_online_cpu(cpu)
+		domain_add_cpu_mon(cpu, r);
+	mutex_unlock(&domain_list_lock);
+	cpus_read_unlock();
 }
 
 enum {
diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index 252a3fd4260c..2f4f8fb317d7 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -238,6 +238,8 @@ static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
 		resctrl_enable_mon_event(e->evts[j].id, true,
 					 e->evts[j].bin_bits, &e->evts[j]);
 
+	pr_info("%s %s monitoring detected\n", r->name, e->name);
+
 	return true;
 }
 
-- 
2.51.0