Hi Tony,
On 8/29/25 12:33 PM, Tony Luck wrote:
> 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.
Above two sentences can be merged into a paragraph.
>
> 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 must
> be queried by name. Add rdt_is_feature_enabled() to check whether quirks
> or kernel command line have disabled a feature.
Above two sentences can be merged into a paragraph.
>
> 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.
>
> Signed-off-by: Tony Luck <tony.luck@intel.com>
>
> starting # with '#' will be ignored, and an empty message
> aborts the commit. # # Date: Mon Aug 11 09:36:45 2025
> -0700 # # On branch rdt-aet-v9-wip # Changes to be committed:
> modified: arch/x86/kernel/cpu/resctrl/core.c # modified:
> arch/x86/kernel/cpu/resctrl/internal.h # # Untracked files: #
> 20250811181709.6241-1-tony.luck@intel.com.mbx # cscope-x86.out #
> cscope-x86.out.in # cscope-x86.out.po # v8/ #
Mangled changelog.
> ---
> .../admin-guide/kernel-parameters.txt | 2 +-
> arch/x86/kernel/cpu/resctrl/internal.h | 2 ++
> arch/x86/kernel/cpu/resctrl/core.c | 30 +++++++++++++++++++
> 3 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 747a55abf494..b600e1b47b0c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6154,7 +6154,7 @@
> rdt= [HW,X86,RDT]
> Turn on/off individual RDT features. List is:
> cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
> - mba, smba, bmec.
> + mba, smba, bmec, energy, perf.
> E.g. to turn on cmt and turn off mba use:
> rdt=cmt,!mba
>
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index b054c7cd13f1..6948803721e4 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -177,6 +177,8 @@ void __init intel_rdt_mbm_apply_quirk(void);
>
> void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>
> +bool rdt_is_feature_enabled(char *name);
> +
> #ifdef CONFIG_X86_CPU_RESCTRL_INTEL_AET
> bool intel_aet_get_events(void);
> void __exit intel_aet_exit(void);
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 5745c6979293..d6e7a9125a10 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -763,6 +763,8 @@ enum {
> RDT_FLAG_MBA,
> RDT_FLAG_SMBA,
> RDT_FLAG_BMEC,
> + RDT_FLAG_ENERGY,
> + RDT_FLAG_PERF,
> };
>
> #define RDT_OPT(idx, n, f) \
> @@ -788,6 +790,8 @@ static struct rdt_options rdt_options[] __ro_after_init = {
> RDT_OPT(RDT_FLAG_MBA, "mba", X86_FEATURE_MBA),
> RDT_OPT(RDT_FLAG_SMBA, "smba", X86_FEATURE_SMBA),
> RDT_OPT(RDT_FLAG_BMEC, "bmec", X86_FEATURE_BMEC),
> + RDT_OPT(RDT_FLAG_ENERGY, "energy", 0),
> + RDT_OPT(RDT_FLAG_PERF, "perf", 0),
> };
> #define NUM_RDT_OPTIONS ARRAY_SIZE(rdt_options)
>
> @@ -837,6 +841,32 @@ bool rdt_cpu_has(int flag)
> return ret;
> }
>
> +/*
> + * Hardware features that do not have X86_FEATURE_* bits.
> + * There is no "hardware does not support this at all" case.
> + * Assume that the caller has already determined that hardware
> + * support is present and just needs to check if the feature has been
> + * disabled by a quirk that has not been overridden by a command
> + * line option.
Another recurring topic. Please do not unnecessarily trim comments to be
so far under 80 columns.
> + */
> +bool rdt_is_feature_enabled(char *name)
> +{
> + struct rdt_options *o;
> + bool ret = true;
> +
> + for (o = rdt_options; o < &rdt_options[NUM_RDT_OPTIONS]; o++) {
> + if (!strcmp(name, o->name)) {
> + if (o->force_off)
> + ret = false;
> + if (o->force_on)
> + ret = true;
> + break;
> + }
> + }
> +
> + return ret;
> +}
> +
> bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt)
> {
> if (!rdt_cpu_has(X86_FEATURE_BMEC))
Reinette