Re: [PATCH v11 11/23] x86/resctrl: Introduce mbm_cntr_cfg to track assignable counters at domain

[James Morse]

Hi Babu,

On 22/01/2025 20:20, 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.

> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 511cfce8fc21..9a54e307d340 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -94,6 +94,18 @@ 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.
> + * @rdtgroup:		 resctrl group assigned to the counter. NULL if the
> + *			 counter is free.
> + */
> +struct mbm_cntr_cfg {
> +	enum resctrl_event_id	evtid;
> +	struct rdtgroup		*rdtgrp;
> +};

struct rdtgroup here suggests this shouldn't be something the arch code is touching.

If its not needed by any arch specific code, (I couldn't find a resctrl_arch helper that
takes this) - could it be moved to resctrl's internal.h.

(If this does need to be visible to the arch code, one option would be to replace rdtgroup
with the closid/rmid, and a valid flag so that memset() continues to reset these entries)


Thanks,

James