linux.git/arch/x86/kernel/cpu/resctrl/core.c, branch v6.18

x86/resctrl: Configure mbm_event mode if supported

2025-09-15T10:52:04+00:00

Configure mbm_event mode on AMD platforms. On AMD platforms, it is
recommended to use the mbm_event mode, if supported, to prevent the
hardware from resetting counters between reads. This can result in
misleading values or display "Unavailable" if no counter is assigned
to the event.

Enable mbm_event mode, known as ABMC (Assignable Bandwidth Monitoring
Counters) on AMD, by default if the system supports it.

Update ABMC across all logical processors within the resctrl domain to
ensure proper functionality.

Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86,fs/resctrl: Detect Assignable Bandwidth Monitoring feature details

2025-09-15T10:08:01+00:00

ABMC feature details are reported via CPUID Fn8000_0020_EBX_x5.
Bits Description
15:0 MAX_ABMC Maximum Supported Assignable Bandwidth
     Monitoring Counter ID + 1

The ABMC feature details are documented in APM [1] available from [2].

  [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
  Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
  Monitoring (ABMC).

Detect the feature and number of assignable counters supported. For backward
compatibility, upon detecting the assignable counter feature, enable the
mbm_total_bytes and mbm_local_bytes events that users are familiar with as
part of original L3 MBM support.

Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 # [2]

x86,fs/resctrl: Consolidate monitoring related data from rdt_resource

2025-09-15T10:07:01+00:00

The cache allocation and memory bandwidth allocation feature properties are
consolidated into struct resctrl_cache and struct resctrl_membw respectively.

In preparation for more monitoring properties that will clobber the existing
resource struct more, re-organize the monitoring specific properties to also
be in a separate structure.

Also convert "bandwidth sources" terminology to "memory transactions" to have
consistency within resctrl for related monitoring features.

  [ bp: Massage commit message. ]

Suggested-by: Reinette Chatre 
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86/resctrl: Add ABMC feature in the command line options

2025-09-15T10:05:23+00:00

Add a kernel command-line parameter to enable or disable the exposure of
the ABMC (Assignable Bandwidth Monitoring Counters) hardware feature to
resctrl.

Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86,fs/resctrl: Prepare for more monitor events

2025-09-15T09:57:03+00:00

There's a rule in computer programming that objects appear zero, once, or many
times. So code accordingly.

There are two MBM events and resctrl is coded with a lot of

  if (local)
          do one thing
  if (total)
          do a different thing

Change the rdt_mon_domain and rdt_hw_mon_domain structures to hold arrays of
pointers to per event data instead of explicit fields for total and local
bandwidth.

Simplify by coding for many events using loops on which are enabled.

Move resctrl_is_mbm_event() to  so it can be used more
widely. Also provide a for_each_mbm_event_id() helper macro.

Cleanup variable names in functions touched to consistently use "eventid" for
those with type enum resctrl_event_id.

Signed-off-by: Tony Luck 
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86/resctrl: Remove the rdt_mon_features global variable

2025-09-15T09:55:50+00:00

rdt_mon_features is used as a bitmask of enabled monitor events. A monitor
event's status is now maintained in mon_evt::enabled with all monitor events'
mon_evt structures found in the filesystem's mon_event_all[] array.

Remove the remaining uses of rdt_mon_features.

Signed-off-by: Tony Luck 
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86,fs/resctrl: Replace architecture event enabled checks

2025-09-15T09:54:14+00:00

The resctrl file system now has complete knowledge of the status of every
event. So there is no need for per-event function calls to check.

Replace each of the resctrl_arch_is_{event}enabled() calls with
resctrl_is_mon_event_enabled(QOS_{EVENT}).

No functional change.

Signed-off-by: Tony Luck 
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86,fs/resctrl: Consolidate monitor event descriptions

2025-09-15T09:46:08+00:00

There are currently only three monitor events, all associated with the
RDT_RESOURCE_L3 resource. Growing support for additional events will be easier
with some restructuring to have a single point in file system code where all
attributes of all events are defined.

Place all event descriptions into an array mon_event_all[]. Doing this has the
beneficial side effect of removing the need for rdt_resource::evt_list.

Add resctrl_event_id::QOS_FIRST_EVENT for a lower bound on range checks for
event ids and as the starting index to scan mon_event_all[].

Drop the code that builds evt_list and change the two places where the list is
scanned to scan mon_event_all[] instead using a new helper macro
for_each_mon_event().

Architecture code now informs file system code which events are available with
resctrl_enable_mon_event().

Signed-off-by: Tony Luck 
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com

x86,fs/resctrl: Remove inappropriate references to cacheinfo in the resctrl subsystem

2025-06-16T19:06:12+00:00

In the resctrl subsystem's Sub-NUMA Cluster (SNC) mode, the rdt_mon_domain
structure representing a NUMA node relies on the cacheinfo interface
(rdt_mon_domain::ci) to store L3 cache information (e.g., shared_cpu_map)
for monitoring. The L3 cache information of a SNC NUMA node determines
which domains are summed for the "top level" L3-scoped events.

rdt_mon_domain::ci is initialized using the first online CPU of a NUMA
node. When this CPU goes offline, its shared_cpu_map is cleared to contain
only the offline CPU itself. Subsequently, attempting to read counters
via smp_call_on_cpu(offline_cpu) fails (and error ignored), returning
zero values for "top-level events" without any error indication.

Replace the cacheinfo references in struct rdt_mon_domain and struct
rmid_read with the cacheinfo ID (a unique identifier for the L3 cache).

rdt_domain_hdr::cpu_mask contains the online CPUs associated with that
domain. When reading "top-level events", select a CPU from
rdt_domain_hdr::cpu_mask and utilize its L3 shared_cpu_map to determine
valid CPUs for reading RMID counter via the MSR interface.

Considering all CPUs associated with the L3 cache improves the chances
of picking a housekeeping CPU on which the counter reading work can be
queued, avoiding an unnecessary IPI.

Fixes: 328ea68874642 ("x86/resctrl: Prepare for new Sub-NUMA Cluster (SNC) monitor files")
Signed-off-by: Qinyun Tan
Signed-off-by: Borislav Petkov (AMD)
Reviewed-by: Reinette Chatre
Tested-by: Tony Luck
Link: https://lore.kernel.org/20250530182053.37502-2-qinyuntan@linux.alibaba.com

Merge tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-05-27T16:53:02+00:00

Pull x86 resource control updates from Borislav Petkov:
 "Carve out the resctrl filesystem-related code into fs/resctrl/ so that
  multiple architectures can share the fs API for manipulating their
  respective hw resource control implementation.

  This is the second step in the work towards sharing the resctrl
  filesystem interface, the next one being plugging ARM's MPAM into the
  aforementioned fs API"

* tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  MAINTAINERS: Add reviewers for fs/resctrl
  x86,fs/resctrl: Move the resctrl filesystem code to live in /fs/resctrl
  x86/resctrl: Always initialise rid field in rdt_resources_all[]
  x86/resctrl: Relax some asm #includes
  x86/resctrl: Prefer alloc(sizeof(*foo)) idiom in rdt_init_fs_context()
  x86/resctrl: Squelch whitespace anomalies in resctrl core code
  x86/resctrl: Move pseudo lock prototypes to include/linux/resctrl.h
  x86/resctrl: Fix types in resctrl_arch_mon_ctx_{alloc,free}() stubs
  x86/resctrl: Move enum resctrl_event_id to resctrl.h
  x86/resctrl: Move the filesystem bits to headers visible to fs/resctrl
  fs/resctrl: Add boiler plate for external resctrl code
  x86/resctrl: Add 'resctrl' to the title of the resctrl documentation
  x86/resctrl: Split trace.h
  x86/resctrl: Expand the width of domid by replacing mon_data_bits
  x86/resctrl: Add end-marker to the resctrl_event_id enum
  x86/resctrl: Move is_mba_sc() out of core.c
  x86/resctrl: Drop __init/__exit on assorted symbols
  x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point
  x86/resctrl: Check all domains are offline in resctrl_exit()
  x86/resctrl: Rename resctrl_sched_in() to begin with "resctrl_arch_"
  ...