linux-kernel - [PATCH v15 24/34] fs/resctrl: Report 'Unassigned' for MBM events in mbm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <296c435e9bf63fc5031114cced00fbb4837ad327.1752013061.git.babu.moger@amd.com>
Date: Tue, 8 Jul 2025 17:17:33 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
	<james.morse@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <x86@...nel.org>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
	<Neeraj.Upadhyay@....com>, <david@...hat.com>, <arnd@...db.de>,
	<fvdl@...gle.com>, <seanjc@...gle.com>, <jpoimboe@...nel.org>,
	<pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
	<manali.shukla@....com>, <babu.moger@....com>, <tao1.su@...ux.intel.com>,
	<sohil.mehta@...el.com>, <kai.huang@...el.com>, <xiaoyao.li@...el.com>,
	<peterz@...radead.org>, <xin3.li@...el.com>, <kan.liang@...ux.intel.com>,
	<mario.limonciello@....com>, <thomas.lendacky@....com>, <perry.yuan@....com>,
	<gautham.shenoy@....com>, <chang.seok.bae@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>
Subject: [PATCH v15 24/34] fs/resctrl: Report 'Unassigned' for MBM events in mbm_event mode

When the "mbm_event" counter assignment mode is enabled, a hardware counter
must be assigned to read the event.

Report 'Unassigned' in case the user attempts to read the event without
assigning a hardware counter.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v15: Updated the changelog.
     Removed the error setting in rdtgroup_mondata_show(). It is already done
     in mon_event_read() based on the discussion.
     https://lore.kernel.org/lkml/b4b14670-9cb0-4f65-abd5-39db996e8da9@intel.com/

v14: Updated the changelog.
     Added the code comment for "-ENOENT" when counter is read without assignement.
     Removed the references to resctrl_is_mbm_event().

v13: Minor commitlog and user doc update.
     Resolved conflicts caused by the recent FS/ARCH code restructure.
     The monitor.c/rdtgroup.c files have been split between the FS and ARCH directories.

v12: Updated the documentation for more clarity.

v11: Domain can be NULL with SNC support so moved the unassign check in
     rdtgroup_mondata_show().

v10: Moved the code to check the assign state inside mon_event_read().
     Fixed few text comments.

v9: Used is_mbm_event() to check the event type.
    Minor user documentation update.

v8: Used MBM_EVENT_ARRAY_INDEX to get the index for the MBM event.
    Documentation update to make the text generic.

v7: Moved the documentation under "mon_data".
    Updated the text little bit.

v6: Added more explaination in the resctrl.rst
    Added checks to detect "Unassigned" before reading RMID.

v5: New patch.
---
 Documentation/filesystems/resctrl.rst | 8 ++++++++
 fs/resctrl/ctrlmondata.c              | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 446736dbd97f..4f5eb5bbd4b5 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -434,6 +434,14 @@ When monitoring is enabled all MON groups will also contain:
 	for the L3 cache they occupy). These are named "mon_sub_L3_YY"
 	where "YY" is the node number.
 
+	The "mbm_event" counter assignment mode offers "num_mbm_cntrs" number of
+	counters and allows users to assign counters to mon_hw_id, event pairs
+	enabling bandwidth monitoring for as long as the counter remains assigned.
+	The hardware will continue tracking the assigned counter until the user
+	manually unassigns it, ensuring that event data is not reset during this
+	period. An MBM event returns 'Unassigned' when the event does not have
+	a hardware counter assigned.
+
 "mon_hw_id":
 	Available only with debug option. The identifier used by hardware
 	for the monitor group. On x86 this is the RMID.
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index ce766b2cdfc1..45351673e4ee 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -661,10 +661,16 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 
 checkresult:
 
+	/*
+	 * -ENOENT is a special case, set only when "mbm_event" counter assignment
+	 * mode is enabled and no counter has been assigned.
+	 */
 	if (rr.err == -EIO)
 		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