[PATCH v14 24/32] x86/resctrl: Add energy/perf choices to rdt boot option

Tony Luck
2025-11-24T18:55:05Z

Legacy resctrl features are enumerated by X86_FEATURE_* flags. These may be
overridden by quirks to disable features in the case of errata. Users can
use kernel command line options to either disable a feature, or to force
enable a feature that was disabled by a quirk.

Provide similar functionality for hardware features that do not have an
X86_FEATURE_* flag. Unlike other features that are tied to X86_FEATURE_*
flags, these are defined by the feature name.

Users may force a feature to be disabled. E.g. "rdt=!perf" will ensure that
none of the perf telemetry events are enabled.

Resctrl architecture code may disable a feature that does not provide full
functionality. Users may override that decision. E.g. "rdt=energy" will
enable any available energy telemetry events even if they do not provide
full functionality.

An optional guid can be included for more granular control of features sharing
a name. E.g. rdt=energy:0x12345 will only override disabling of the energy
feature with guid = 0x12345.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
.../admin-guide/kernel-parameters.txt | 6 ++-
arch/x86/kernel/cpu/resctrl/internal.h | 2 +
arch/x86/kernel/cpu/resctrl/core.c | 2 +
arch/x86/kernel/cpu/resctrl/intel_aet.c | 37 +++++++++++++++++++
4 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8c5636a120ee..e47def4a3dd8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6207,9 +6207,13 @@
rdt= [HW,X86,RDT]
Turn on/off individual RDT features. List is:
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
- mba, smba, bmec, abmc, sdciae.
+ mba, smba, bmec, abmc, sdciae, energy[:guid],
+ perf[:guid].
E.g. to turn on cmt and turn off mba use:
rdt=cmt,!mba
+ To turn off all energy features and ensure that
+ the 0x12345 perf feature is enabled use:
+ rdt=!energy,perf:0x12345

reboot= [KNL]
Format (x86 or x86_64):
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 0b7f8317be14..304e6e341905 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -236,6 +236,7 @@ void __exit intel_aet_exit(void);
int intel_aet_read_event(int domid, u32 rmid, void *arch_priv, u64 *val);
void intel_aet_mon_domain_setup(int cpu, int id, struct rdt_resource *r,
struct list_head *add_pos);
+bool intel_aet_option(bool force_off, char *tok);
#else
static inline bool intel_aet_get_events(void) { return false; }
static inline void __exit intel_aet_exit(void) { }
@@ -246,6 +247,7 @@ static inline int intel_aet_read_event(int domid, u32 rmid, void *arch_priv, u64

static inline void intel_aet_mon_domain_setup(int cpu, int id, struct rdt_resource *r,
struct list_head *add_pos) { }
+static inline bool intel_aet_option(bool force_off, char *tok) { return false; }
#endif

#endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 283d653002a2..960974ffa866 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -820,6 +820,8 @@ static int __init set_rdt_options(char *str)
force_off = *tok == '!';
if (force_off)
tok++;
+ if (intel_aet_option(force_off, tok))
+ continue;
for (o = rdt_options; o < &rdt_options[NUM_RDT_OPTIONS]; o++) {
if (strcmp(tok, o->name) == 0) {
if (force_off)
diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index 46c64419ec10..50c8b4c50790 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -57,12 +57,16 @@ struct pmt_event {
* struct event_group - Events with the same feature type ("energy" or "perf") and guid.
* @feature: Type of events, for example FEATURE_PER_RMID_PERF_TELEM or
* FEATURE_PER_RMID_ENERGY_TELEM, in this group.
+ * @name: Name for this group (used by boot rdt= option)
* @pfg: Points to the aggregated telemetry space information
* returned by the intel_pmt_get_regions_by_feature()
* call to the INTEL_PMT_TELEMETRY driver that contains
* data for all telemetry regions type @feature.
* Valid if the system supports the event group.
* NULL otherwise.
+ * @force_off: True when "rdt" command line disables this @guid.
+ * @force_on: True when "rdt" command line overrides disable of
+ * this @guid due to insufficient @num_rmid.
* @guid: Unique number per XML description file.
* @mmio_size: Number of bytes of MMIO registers for this group.
* @num_events: Number of events in this group.
@@ -71,7 +75,9 @@ struct pmt_event {
struct event_group {
/* Data fields for additional structures to manage this group. */
enum pmt_feature_id feature;
+ char *name;
struct pmt_feature_group *pfg;
+ bool force_off, force_on;

/* Remaining fields initialized from XML file. */
u32 guid;
@@ -89,6 +95,7 @@ struct event_group {
*/
static struct event_group energy_0x26696143 = {
.feature = FEATURE_PER_RMID_ENERGY_TELEM,
+ .name = "energy",
.guid = 0x26696143,
.mmio_size = XML_MMIO_SIZE(576, 2, 3),
.num_events = 2,
@@ -104,6 +111,7 @@ static struct event_group energy_0x26696143 = {
*/
static struct event_group perf_0x26557651 = {
.feature = FEATURE_PER_RMID_PERF_TELEM,
+ .name = "perf",
.guid = 0x26557651,
.mmio_size = XML_MMIO_SIZE(576, 7, 3),
.num_events = 7,
@@ -128,6 +136,32 @@ static struct event_group *known_event_groups[] = {
_peg < &known_event_groups[ARRAY_SIZE(known_event_groups)]; \
_peg++)

+bool intel_aet_option(bool force_off, char *tok)
+{
+ struct event_group **peg;
+ bool ret = false;
+ u32 guid = 0;
+ char *name;
+
+ name = strsep(&tok, ":");
+ if (tok && kstrtou32(tok, 16, &guid))
+ return false;
+
+ for_each_event_group(peg) {
+ if (strcmp(name, (*peg)->name))
+ continue;
+ if (guid && (*peg)->guid != guid)
+ continue;
+ if (force_off)
+ (*peg)->force_off = true;
+ else
+ (*peg)->force_on = true;
+ ret = true;
+ }
+
+ return ret;
+}
+
/*
* Clear the address field of regions that did not pass the checks in
* skip_telem_region() so they will not be used by intel_aet_read_event().
@@ -178,6 +212,9 @@ static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
{
int skipped_events = 0;

+ if (e->force_off)
+ return false;
+
if (!group_has_usable_regions(e, p))
return false;

--
2.51.1