linux-toradex.git/fs/resctrl, branch master

fs/resctrl: Ensure default group reports tasks on monitor-only systems

2026-10-10T00:43:05+00:00

resctrl can be mounted on a system that supports monitoring but not allocation.

On such a system reading the "tasks" file in the default group reports no
tasks, even when there are tasks assigned to the default group. This problem
occurs because the check for whether a task belongs to a CTRL_MON group is
gated by a check for whether the system supports allocation.

The resctrl_arch_alloc_capable() check in is_closid_match() breaks task
reporting for the default group on monitor-only systems so remove this check.
On systems that support allocation the check is redundant.

Fixes: e6b2fac36fcc ("x86/resctrl: Use is_closid_match() in more places")
Closes: https://sashiko.dev/#/patchset/20260831174421.13921-1-tony.luck%40intel.com?part=9
Reported-by: Sashiko 
Signed-off-by: Tony Luck 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://patch.msgid.link/20261009193923.15498-1-tony.luck@intel.com

x86,fs/resctrl: Add event group descriptions for Intel Diamond Rapids

2026-10-01T05:47:08+00:00

Intel Diamond Rapids exposes Application Energy Telemetry through two new PMT
aggregator GUIDs: one covering the "energy" feature, and one covering the
"perf" feature, both documented in the Intel-PMT XML repository at
https://github.com/intel/Intel-PMT

The "perf" aggregator references two events not previously enumerated by
resctrl: retired instructions (INST_RETIRED), and a count of unhalted core
clock cycles perceived by hardware as contributing to instruction execution
(PCNT).

Add definitions for both aggregators, and add the two new events to the
resctrl filesystem so they can be exposed to user space.

Signed-off-by: Tony Luck 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://patch.msgid.link/20260930171554.12794-1-tony.luck@intel.com

fs/resctrl: Simplify pseudo_lock_measure_trigger()

2026-09-17T19:08:47+00:00

Use convenient kstrtoint_from_user() to simplify pseudo_lock_measure_trigger().

No functional changes.

Signed-off-by: Dmitry Antipov 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://patch.msgid.link/20260821081128.19242-2-dmantipov@yandex.ru

fs/resctrl: Avoid extra call to strlen() in schemata_list_add()

2026-09-17T17:41:53+00:00

After passing an overflow check, it's safe to assume that snprintf()
returns the number of characters emitted. So drop the unnecessary
call to strlen().

Signed-off-by: Dmitry Antipov 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://patch.msgid.link/20260821081128.19242-1-dmantipov@yandex.ru

fs/resctrl: Factor MBA parse-time conversion to be per-arch

2026-09-14T15:20:25+00:00

The control value parser for the MB resource currently coerces the memory
bandwidth percentage value from userspace to be an exact multiple of the
rdt_resource::resctrl_membw::bw_gran parameter.

On MPAM systems, this results in somewhat worse-than-worst-case rounding, since
the bandwidth granularity advertised to resctrl by the MPAM driver is in general
only an approximation to the actual hardware granularity on these systems, and
the hardware bandwidth allocation control value is not natively a percentage --
necessitating a further conversion in the resctrl_arch_update_domains() path,
regardless of the conversion done at parse time.

For MPAM and x86 use their custom pre-prepared parse-time conversion,
resctrl_arch_preconvert_bw(). This will avoid accumulated error from rounding
the value twice on MPAM systems. For x86 systems there is no functional change.

Clarify the documentation, but avoid overly exact promises.

Clamping to bw_min and bw_max still feels generic: leave it in the core code,
for now.

Signed-off-by: Dave Martin 
Signed-off-by: Ben Horgan 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Ben Horgan 
Reviewed-by: Reinette Chatre 
Reviewed-by: Gavin Shan 
Link: https://patch.msgid.link/20260911163613.1131447-4-ben.horgan@arm.com

fs/resctrl: Inform user space when status buffer overflowed

2026-07-27T04:40:26+00:00

resctrl fs commands are becoming more powerful with, for example, a user able
to use syntax like '*' to make broad configuration changes. Such commands that
span multiple domains may result in more than one message printed to the
last_cmd_status buffer with more planned.

Issue "[truncated]" when displaying the last_cmd_status buffer to communicate
if it overflowed. Upon encountering this, user space is expected to combine
details about the failure found in info/last_cmd_status with related resctrl
files to learn the accurate system state after the command failure.

Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Ben Horgan 
Reviewed-by: Tony Luck 
Tested-by: Babu Moger 
Link: https://patch.msgid.link/eb3d1aaa41d1f2bf6b1bb26ceafd52f04912121d.1782857711.git.reinette.chatre@intel.com

fs/resctrl: Communicate resource group deleted error via last_cmd_status

2026-07-27T04:28:31+00:00

User space expects last_cmd_status to contain additional information if any
resctrl command fails.

A resctrl command may be blocked on the rdtgroup_mutex waiting for another
command to finish and find that once the mutex is available that the resource
group has since been deleted.

In this scenario the command will fail while last_cmd_status contains either
"ok" if the last_cmd_status buffer is empty or an outdated error from
a previous command failure if last_cmd_status buffer has content.

Include clearing of last_cmd_status buffer as part of rdtgroup_kn_lock_live()
that is used to obtain access and needed locking to a resource group before
attempting a command on the group.

With the last_cmd_status buffer ready, provide an appropriate message to user
space if the resource group has been deleted.

No last_cmd_status treatment is needed for the remaining failure of
rdtgroup_kn_lock_live() encountering a non-existent resource group since that
could only occur during an attempt to obtain a resource group lock on a file
in info/ which is an invalid usage.

Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Tony Luck 
Tested-by: Babu Moger 
Link: https://patch.msgid.link/9982141ec6f3ec18e0c53d7feabb19651583cf0e.1782857711.git.reinette.chatre@intel.com

fs/resctrl: Add last_cmd_status support for writes to max_threshold_occupancy

2026-07-27T04:22:37+00:00

info/last_cmd_status is intended to contain more information if a write to
any resctrl file fails. Writes to max_threshold_occupancy did not receive
last_cmd_status support during initial last_cmd_status enabling. Add it now.

Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Tony Luck 
Tested-by: Babu Moger 
Link: https://patch.msgid.link/dfc60cf5324e15612db075b0987bd89c490fbad5.1782857711.git.reinette.chatre@intel.com

fs/resctrl: Change last_cmd_status custom during input parsing

2026-07-26T20:09:41+00:00

A pattern of usage of last_cmd_status was introduced during its enabling in
commit

  c377dcfbee80 ("x86/intel_rdt: Add diagnostics when writing the schemata file")

and since copied throughout resctrl to result in the following custom:

  ..._write()
  {
  	/* Early parsing of input, exit on failure. */

  	/* Obtain rdtgroup_mutex */
  	rdt_last_cmd_clear(); /* Clear last_cmd_status buffer */

  	/*
  	 * Act on user command, failures result in detail
  	 * error message in last_cmd_status buffer via
  	 * rdt_last_cmd_puts()/rdt_last_cmd_printf().
  	 */

  	/* Release rdtgroup_mutex */
  }

If resctrl exits with failure during early parsing of input there are two
possible scenarios:

 - The last_cmd_status buffer is empty and a user's read of
   info/last_cmd_status returns "ok".

 - The last_cmd_status buffer contains details from an earlier ...write()
   failure and a user's read of info/last_cmd_status returns this outdated
   error description.

Writing to a resctrl file is considered a "resctrl command" and the resctrl
documentation states the following about the last_cmd_status file:

  "If the command failed, it will provide more information that can be
   conveyed in the error returns from file operations."

Neither of the current scenarios is correct behavior.

Move early input parsing to be done with rdtgroup_mutex held after the
last_cmd_status buffer is cleared. Let info/last_cmd_status be accurate
when an error is encountered during parsing of user command.

Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Ben Horgan 
Reviewed-by: Tony Luck 
Tested-by: Babu Moger 
Link: https://patch.msgid.link/c9eba0ef3b9a72b845b4ae02ecd7c098ed8bf06f.1782857711.git.reinette.chatre@intel.com

fs/resctrl: Use accurate and symmetric exit flows

2026-07-25T20:50:02+00:00

During schemata file write handling there is one error exit path labeled
"out" that handles all cleanup and unlocking needed on exit. The staged
configs cleared during an error exit may not have been used at the time
of exit making the clearing of the staged configs unnecessary.

Access the exit code using two labels and only clear the staged
configuration if it was in use at the time of exit. Doing so makes the
code flow obvious and simplifies upcoming changes that improve the
handling of failures during early input parsing.

Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Tony Luck 
Tested-by: Babu Moger 
Link: https://patch.msgid.link/4cdd79d612dc6d62ccd490e1c31298025d66d385.1782857711.git.reinette.chatre@intel.com