Re: [PATCH v14 16/32] x86,fs/resctrl: Introduce event configuration field in struct mon_evt

[Reinette Chatre]

Hi Babu,

On 6/13/25 2:05 PM, Babu Moger wrote:
> When supported, mbm_assign_mode allows the user to configure events to
> track specific types of memory transactions.

Since there is also a "default" mbm_assign_mode this should be made specific
to mbm_event.

> 
> Introduce the evt_cfg field in struct mon_evt to define the type of memory
> transactions tracked by a monitoring event. Also add helper functions to
> get and set the evt_cfg value.

hmmm ... this does not sound right (more below)

> 
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> v14: This is updated patch from previous patch.
>      https://lore.kernel.org/lkml/95b7f4e9d72773e8fda327fc80b429646efc3a8a.1747349530.git.babu.moger@xxxxxxx/
>      Removed mbm_mode as it is not required anymore.
>      Added resctrl_get_mon_evt_cfg() and resctrl_set_mon_evt_cfg().
> 
> v13: New patch to handle different event configuration types with
>      mbm_cntr_assign mode.
> ---
>  arch/x86/kernel/cpu/resctrl/core.c |  4 ++++
>  fs/resctrl/internal.h              |  4 ++++
>  fs/resctrl/monitor.c               | 10 ++++++++++
>  include/linux/resctrl.h            |  3 +++
>  4 files changed, 21 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 01b210febc7d..1df171d04bea 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -875,10 +875,14 @@ static __init bool get_rdt_mon_resources(void)
>  	}
>  	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_TOTAL) || rdt_cpu_has(X86_FEATURE_ABMC)) {
>  		resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID);
> +		resctrl_set_mon_evt_cfg(QOS_L3_MBM_TOTAL_EVENT_ID, MAX_EVT_CONFIG_BITS);
>  		ret = true;
>  	}
>  	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_LOCAL) || rdt_cpu_has(X86_FEATURE_ABMC)) {
>  		resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
> +		resctrl_set_mon_evt_cfg(QOS_L3_MBM_LOCAL_EVENT_ID,
> +					READS_TO_LOCAL_MEM | READS_TO_LOCAL_S_MEM |
> +					NON_TEMP_WRITE_TO_LOCAL_MEM);
>  		ret = true;
>  	}

The architecture should have no business setting the event configuration. This should
all be managed via resctrl fs, no? I think the resctrl_set_mon_evt_cfg() helper should
be dropped. The above initialization can be done as part of mon_event_all[] initialization
within resctrl.

>  
> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
> index 20e2c45cea64..71059c2cda16 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -56,6 +56,9 @@ static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
>   * @evtid:		event id
>   * @rid:		index of the resource for this event
>   * @name:		name of the event
> + * @@evt_cfg:		Event configuration value that represents the

Extra @ in "@@evt_cfg"

> + *			memory transactions (e.g., READS_TO_LOCAL_MEM,
> + *			READS_TO_REMOTE_MEM) being tracked by @evtid.

Can append "Only valid if @evtid is an MBM event."

>   * @configurable:	true if the event is configurable
>   * @enabled:		true if the event is enabled
>   */
> @@ -63,6 +66,7 @@ struct mon_evt {
>  	enum resctrl_event_id	evtid;
>  	enum resctrl_res_level	rid;
>  	char			*name;
> +	u32			evt_cfg;
>  	bool			configurable;
>  	bool			enabled;
>  };
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 2893da994f3c..3e1a8239b0d3 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -884,6 +884,16 @@ bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid)
>  	       mon_event_all[eventid].enabled;
>  }
>  
> +u32 resctrl_get_mon_evt_cfg(enum resctrl_event_id evtid)
> +{
> +	return mon_event_all[evtid].evt_cfg;
> +}
> +
> +void resctrl_set_mon_evt_cfg(enum resctrl_event_id evtid, u32 evt_cfg)
> +{
> +	mon_event_all[evtid].evt_cfg = evt_cfg;
> +}
> +
>  /**
>   * resctrl_mon_resource_init() - Initialise global monitoring structures.
>   *
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 468a4ebabc64..a58dd40b7246 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -413,6 +413,9 @@ static inline bool resctrl_is_mbm_event(enum resctrl_event_id eventid)
>  		eventid <= QOS_L3_MBM_LOCAL_EVENT_ID);
>  }
>  
> +u32 resctrl_get_mon_evt_cfg(enum resctrl_event_id eventid);
> +void resctrl_set_mon_evt_cfg(enum resctrl_event_id eventid, u32 evt_cfg);

I think resctrl_set_mon_evt_cfg() should be dropped. Any changes to mon_evt:evt_cfg
should be via resctrl, either via initialization (all archs should use same default)
or when user writes to the event configuration's file.

> +
>  #define for_each_mbm_event_id(eventid)				\
>  	for (eventid = QOS_L3_MBM_TOTAL_EVENT_ID;		\
>  	     eventid <= QOS_L3_MBM_LOCAL_EVENT_ID; eventid++)

sidenote: This change looks to be a good foundation to bring back the BMEC optimization
you worked on earlier where it is no longer needed to read event configuration from
hardware.

Reinette