linux-kernel - [PATCH v11 12/23] x86/resctrl: Introduce interface to display number of free counters

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Message-ID: <f60eced8c7b81267b0067b0c41a4ddbc263ded5b.1737577229.git.babu.moger@amd.com>
Date: Wed, 22 Jan 2025 14:20:20 -0600
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <reinette.chatre@...el.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
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CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
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Subject: [PATCH v11 12/23] x86/resctrl: Introduce interface to display number of free counters

Provide the interface to display the number of monitoring counters
available for assignment in each domain when mbm_cntr_assign is enabled.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v11: Rename rdtgroup_available_mbm_cntrs_show() to resctrl_available_mbm_cntrs_show().
     Few minor text changes.

v10: Patch changed to handle the counters at domain level.
     https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
     So, display logic also changed now.

v9: New patch
---
 Documentation/arch/x86/resctrl.rst     |  8 +++++
 arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 46 ++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 31ff764deeeb..99cae75559b0 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -299,6 +299,14 @@ with the following files:
 	memory bandwidth tracking to a single memory bandwidth event per
 	monitoring group.
 
+"available_mbm_cntrs":
+	The number of monitoring counters available for assignment in each
+	domain when mbm_cntr_assign mode is enabled on the system.
+	::
+
+	 # cat /sys/fs/resctrl/info/L3_MON/available_mbm_cntrs
+	 0=30;1=30
+
 "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/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 6fe9e610e9a0..f2bf5b13465d 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1234,6 +1234,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 			cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
 			r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
 			resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
+			resctrl_file_fflags_init("available_mbm_cntrs", RFTYPE_MON_INFO);
 		}
 	}
 
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 75a3b56996ca..2b86124c336b 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -888,6 +888,46 @@ static int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
+					    struct seq_file *s, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+	struct rdt_mon_domain *dom;
+	bool sep = false;
+	u32 cntrs, i;
+	int ret = 0;
+
+	cpus_read_lock();
+	mutex_lock(&rdtgroup_mutex);
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_cntr_assign mode is not enabled\n");
+		ret = -EINVAL;
+		goto unlock_cntrs_show;
+	}
+
+	list_for_each_entry(dom, &r->mon_domains, hdr.list) {
+		if (sep)
+			seq_puts(s, ";");
+
+		cntrs = 0;
+		for (i = 0; i < r->mon.num_mbm_cntrs; i++) {
+			if (!dom->cntr_cfg[i].rdtgrp)
+				cntrs++;
+		}
+
+		seq_printf(s, "%d=%d", dom->hdr.id, cntrs);
+		sep = true;
+	}
+	seq_puts(s, "\n");
+
+unlock_cntrs_show:
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+
+	return ret;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1916,6 +1956,12 @@ static struct rftype res_common_files[] = {
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= resctrl_num_mbm_cntrs_show,
 	},
+	{
+		.name		= "available_mbm_cntrs",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= resctrl_available_mbm_cntrs_show,
+	},
 	{
 		.name		= "cpus",
 		.mode		= 0644,
-- 
2.34.1