linux-kernel - [PATCH v6 18/22] x86/resctrl: Report "Unassigned" for MBM events in ABMC mode

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Message-ID: <5906d1a910c5e2bceb680c874e5e391618f6e313.1722981659.git.babu.moger@amd.com>
Date: Tue, 6 Aug 2024 17:00:55 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <fenghua.yu@...el.com>, <reinette.chatre@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <babu.moger@....com>, <kim.phillips@....com>,
	<lukas.bulwahn@...il.com>, <seanjc@...gle.com>, <jmattson@...gle.com>,
	<leitao@...ian.org>, <jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: [PATCH v6 18/22] x86/resctrl: Report "Unassigned" for MBM events in ABMC mode

In ABMC mode, the hardware counter should be assigned to read the MBM
events.

Report "Unassigned" in case the user attempts to read the events without
assigning the counter.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v6: Added more explaination in the resctrl.rst
    Added checks to detect "Unassigned" before reading RMID.

v5: New patch.
---
 Documentation/arch/x86/resctrl.rst        | 11 +++++++++++
 arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 13 ++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index fe9f10766c4f..aea440ee6107 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -294,6 +294,17 @@ with the following files:
 "num_mbm_cntrs":
 	The number of monitoring counters available for assignment.
 
+	Resctrl subsystem provides the interface to count maximum of two
+	MBM events per group, from a combination of total and local events.
+	Keeping the current interface, users can assign a maximum of two
+	monitoring counters per group. User will also have the option to
+	enable only one counter to the group.
+
+	With limited number of counters, system can run out of assignable counters.
+	In mbm_cntr_assign mode, the MBM event counters will return "Unassigned" if
+	the counter is not assigned to the event when read. Users need to assign a
+	counter manually to read the events.
+
 "max_threshold_occupancy":
 		Read/write file provides the largest value (in
 		bytes) at which a previously used LLC_occupancy
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 50fa1fe9a073..ea918ce7c3ef 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -562,7 +562,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 	struct rdtgroup *rdtgrp;
 	struct rdt_resource *r;
 	union mon_data_bits md;
-	int ret = 0;
+	int ret = 0, index;
 
 	rdtgrp = rdtgroup_kn_lock_live(of->kn);
 	if (!rdtgrp) {
@@ -576,6 +576,15 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 	evtid = md.u.evtid;
 	r = &rdt_resources_all[resid].r_resctrl;
 
+	if (resctrl_arch_get_abmc_enabled() && evtid != QOS_L3_OCCUP_EVENT_ID) {
+		index = mon_event_config_index_get(evtid);
+		if (index != INVALID_CONFIG_INDEX &&
+		    rdtgrp->mon.cntr_id[index] == MON_CNTR_UNSET) {
+			rr.err = -ENOENT;
+			goto checkresult;
+		}
+	}
+
 	if (md.u.sum) {
 		/*
 		 * This file requires summing across all domains that share
@@ -613,6 +622,8 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 		seq_puts(m, "Error\n");
 	else if (rr.err == -EINVAL)
 		seq_puts(m, "Unavailable\n");
+	else if (rr.err == -ENOENT)
+		seq_puts(m, "Unassigned\n");
 	else
 		seq_printf(m, "%llu\n", rr.val);
 
-- 
2.34.1