Re: [PATCH v13 08/27] x86/resctrl: Introduce mbm_cntr_cfg to track assignable counters at domain

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

shortlog: "at domain" -> "per domain"?

On 5/15/25 3:51 PM, Babu Moger wrote:
> In mbm_cntr_assign mode hardware counters are assigned/unassigned to an
> MBM event of a monitor group. Hardware counters are assigned/unassigned
> at monitoring domain level.
> 
> Manage a monitoring domain's hardware counters using a per monitoring
> domain array of struct mbm_cntr_cfg that is indexed by the hardware
> counter ID. A hardware counter's configuration contains the MBM event
> ID and points to the monitoring group that it is assigned to, with a
> NULL pointer meaning that the hardware counter is available for assignment.
> 
> There is no direct way to determine which hardware counters are assigned
> to a particular monitoring group. Check every entry of every hardware
> counter configuration array in every monitoring domain to query which
> MBM events of a monitoring group is tracked by hardware. Such queries are
> acceptable because of a very small number of assignable counters (32
> to 64).
> 
> Suggested-by: Peter Newman <peternewman@google.com>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> v13: Resolved conflicts caused by the recent FS/ARCH code restructure.
>      The files monitor.c/rdtgroup.c have been split between FS and ARCH directories.
> 
> v12: Fixed the struct mbm_cntr_cfg code documentation.
>      Removed few strange charactors in changelog.
>      Added the counter range for better understanding.
>      Moved the struct mbm_cntr_cfg definition to resctrl/internal.h as
>      suggested by James.
> 
> v11: Refined the change log based on Reinette's feedback.
>      Fixed few style issues.
> 
> v10: Patch changed completely to handle the counters at domain level.
>      https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
>      Removed Reviewed-by tag.
>      Did not see the need to add cntr_id in mbm_state structure. Not used in the code.
> 
> v9: Added Reviewed-by tag. No other changes.
> 
> v8: Minor commit message changes.
> 
> v7: Added check mbm_cntr_assignable for allocating bitmap mbm_cntr_map
> 
> v6: New patch to add domain level assignment.
> ---
>  fs/resctrl/rdtgroup.c   | 11 +++++++++++
>  include/linux/resctrl.h | 16 ++++++++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 51f8f8d3ccbc..e2005fc9acd9 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -4085,6 +4085,7 @@ static void rdtgroup_setup_default(void)
>  
>  static void domain_destroy_mon_state(struct rdt_mon_domain *d)
>  {
> +	kfree(d->cntr_cfg);
>  	bitmap_free(d->rmid_busy_llc);
>  	kfree(d->mbm_total);
>  	kfree(d->mbm_local);
> @@ -4171,6 +4172,16 @@ static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_mon_domain
>  			return -ENOMEM;
>  		}
>  	}
> +	if (resctrl_is_mbm_enabled() && r->mon.mbm_cntr_assignable) {
> +		tsize = sizeof(*d->cntr_cfg);
> +		d->cntr_cfg = kcalloc(r->mon.num_mbm_cntrs, tsize, GFP_KERNEL);
> +		if (!d->cntr_cfg) {
> +			bitmap_free(d->rmid_busy_llc);
> +			kfree(d->mbm_total);
> +			kfree(d->mbm_local);
> +			return -ENOMEM;
> +		}
> +	}
>  
>  	return 0;
>  }
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index bdb264875ef6..d77981d1fcb9 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -156,6 +156,20 @@ struct rdt_ctrl_domain {
>  	u32				*mbps_val;
>  };
>  
> +/**
> + * struct mbm_cntr_cfg - Assignable counter configuration
> + * @evtid:		MBM event to which the counter is assigned. Only valid
> + *			if @rdtgroup is not NULL.
> + * @evt_cfg:		Event configuration value.

@evt_cfg is not introduced in changelog nor defined here. Please add a snippet here
on what @evt_cfg's values represent. This is important since this is exposed
as resctrl fs API to architectures so all architectures need to use same values when
interacting with resctrl.

> + * @rdtgrp:		resctrl group assigned to the counter. NULL if the
> + *			counter is free.
> + */
> +struct mbm_cntr_cfg {
> +	enum resctrl_event_id   evtid;
> +	u32                     evt_cfg;
> +	struct rdtgroup         *rdtgrp;

Please align struct member names using TABs.

> +};
> +
>  /**
>   * struct rdt_mon_domain - group of CPUs sharing a resctrl monitor resource
>   * @hdr:		common header for different domain types
> @@ -167,6 +181,7 @@ struct rdt_ctrl_domain {
>   * @cqm_limbo:		worker to periodically read CQM h/w counters
>   * @mbm_work_cpu:	worker CPU for MBM h/w counters
>   * @cqm_work_cpu:	worker CPU for CQM h/w counters
> + * @cntr_cfg:		assignable counters configuration

"array of assignable counters' configuration (indexed by counter ID)"

>   */
>  struct rdt_mon_domain {
>  	struct rdt_domain_hdr		hdr;
> @@ -178,6 +193,7 @@ struct rdt_mon_domain {
>  	struct delayed_work		cqm_limbo;
>  	int				mbm_work_cpu;
>  	int				cqm_work_cpu;
> +	struct mbm_cntr_cfg		*cntr_cfg;
>  };
>  
>  /**

Reinette