Re: [PATCH v13 20/27] x86/resctrl: Provide interface to update the event configurations

["Moger, Babu" <bmoger@amd.com>]

Hi Reinette,

On 5/22/2025 11:45 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/15/25 3:52 PM, Babu Moger wrote:
>> Users can modify the event configuration by writing to the event_filter
>> interface file. The event configurations for mbm_cntr_assign mode are
>> located in /sys/fs/resctrl/info/event_configs/.
> 
> heh ... looks like you also started thinking that "event_configs"
> is a better name (also missing L3_MON).

Interesting... 'event_configs' seems to have made its way in somehow.
Alright, I’ll go ahead and add L3_MON."

> 
>>
>> Update the assignments of all groups when the event configuration is
>> modified.
>>
>> Example:
>> $ cd /sys/fs/resctrl/
>>
>> $ cat info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>>    local_reads,local_non_temporal_writes,local_reads_slow_memory
>>
>> $ echo "local_reads,local_non_temporal_writes" >
>>    info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>
>> $ cat info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>    local_reads,local_non_temporal_writes
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>> v13: Updated changelog for imperative mode.
>>       Added function description in the prototype.
>>       Updated the user doc resctrl.rst to address few feedback.
>>       Resolved conflicts caused by the recent FS/ARCH code restructure.
>>       The rdtgroup.c/monitor.c file has now been split between the FS and ARCH directories.
>>
>> v12: New patch to modify event configurations.
>> ---
>>   Documentation/filesystems/resctrl.rst |  12 +++
>>   fs/resctrl/rdtgroup.c                 | 120 +++++++++++++++++++++++++-
>>   2 files changed, 131 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index 4eb9f007ba3d..9923276826db 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
> 
> ...
> 
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index cf84e3a382ac..8c498b41be5d 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -1930,6 +1930,123 @@ static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq,
>>   	return 0;
>>   }
>>   
>> +/**
>> + * resctrl_group_assign - Update the counter assignments for the event in
>> + *			  a group.
> 
> This name is very generic with an unexpected namespace. "rdtgroup_" prefix
> is often used for a function that operates on a rdtgroup. This can thus be
> "rdtgroup_assign_cntr()".

Sure.

> 
>> + * @r:		Resource to which update needs to be done.
>> + * @rdtgrp:	Resctrl group.
>> + * @evtid:	Event ID.
>> + * @evt_cfg:	Event configuration value.
>> + */
>> +static int resctrl_group_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
>> +				enum resctrl_event_id evtid, u32 evt_cfg)
>> +{
>> +	struct rdt_mon_domain *d;
>> +	int cntr_id;
>> +
>> +	list_for_each_entry(d, &r->mon_domains, hdr.list) {
>> +		cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
>> +		if (cntr_id >= 0 && d->cntr_cfg[cntr_id].evt_cfg != evt_cfg) {
>> +			d->cntr_cfg[cntr_id].evt_cfg = evt_cfg;
>> +			resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
>> +						 rdtgrp->closid, cntr_id, evt_cfg, true);
>> +		}
>> +	}
>> +
>> +	return 0;
> 
> Can just return void?

sure.

> 
>> +}
>> +
>> +/**
>> + * resctrl_update_assign - Update the counter assignments for the event for all
>> + *			   the groups.
> 
> Again very generic with "update" and "assign" that seem redundant? How about
> "resctrl_assign_cntr_allrdtgrp()"?

Yes.

> 
>> + * @r:		Resource to which update needs to be done.
>> + * @evtid:	Event ID.
>> + * @evt_cfg:	Event configuration value.
> 
> Why are both event ID and evt_cfg needed? Could just passing mon_evt simplify this?
> 
>> + */
>> +static int resctrl_update_assign(struct rdt_resource *r, enum resctrl_event_id evtid,
>> +				 u32 evt_cfg)
>> +{
>> +	struct rdtgroup *prgrp, *crgrp;
>> +
>> +	/* Check if the cntr_id is associated to the event type updated */
> 
> Comment does not match code.

Will correct it.

> 
>> +	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
>> +		resctrl_group_assign(r, prgrp, evtid, evt_cfg);
>> +
>> +		list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list) {
>> +			resctrl_group_assign(r, crgrp, evtid, evt_cfg);
>> +		}
> 
> Unnecessary braces?

Yes.

> 
>> +	}
>> +
>> +	return 0;
> 
> return void?
> 

Sure.

>> +}
>> +
>> +static int resctrl_process_configs(char *tok, u32 *val)
>> +{
>> +	char *evt_str;
>> +	bool found;
>> +	int i;
>> +
>> +next_config:
>> +	if (!tok || tok[0] == '\0')
>> +		return 0;
>> +
>> +	/* Start processing the strings for each event type */
> 
> Does comment intend to describe one iteration or all iterations?
> Also, "event type" -> "memory transaction"?

Sure.

> 
>> +	evt_str = strim(strsep(&tok, ","));
>> +	found = false;
>> +	for (i = 0; i < NUM_MBM_EVT_VALUES; i++) {
>> +		if (!strcmp(mbm_evt_values[i].evt_name, evt_str)) {
>> +			*val |=  mbm_evt_values[i].evt_val;
> 
> check spacing.

ok.

> 
>> +			found = true;
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (!found) {
>> +		rdt_last_cmd_printf("Invalid event type %s\n", evt_str);
>> +		return -EINVAL;
> 
> Looks like this will return partially initialized data. Please use a local
> variable in which to gather the new configuration and only assign that
> to provided pointer on success.

Yes. Makes sense.

> 
>> +	}
>> +
>> +	goto next_config;
>> +}
>> +
>> +static ssize_t event_filter_write(struct kernfs_open_file *of, char *buf,
>> +				  size_t nbytes, loff_t off)
>> +{
>> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>> +	struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
>> +	u32 evt_cfg = 0;
>> +	int ret = 0;
>> +
>> +	/* Valid input requires a trailing newline */
>> +	if (nbytes == 0 || buf[nbytes - 1] != '\n')
>> +		return -EINVAL;
>> +
>> +	buf[nbytes - 1] = '\0';
>> +
>> +	cpus_read_lock();
>> +	mutex_lock(&rdtgroup_mutex);
>> +
>> +	rdt_last_cmd_clear();
>> +
>> +	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
>> +		rdt_last_cmd_puts("mbm_cntr_assign mode is not enabled\n");
>> +		ret = -EINVAL;
>> +		goto unlock_out;
> 
> "grep goto fs/resctrl/rdtgroup.c"

Will change it to "out_unlock".

> 
>> +	}
>> +
>> +	ret = resctrl_process_configs(buf, &evt_cfg);
>> +	if (!ret && mevt->evt_val != evt_cfg) {
>> +		mevt->evt_val = evt_cfg;
> 
> ah ... here it is. hmmm ... but it is mon_evt::evt_cfg, no? ah,
> fixed in next patch.

Yea. My bad.

> 
> I still seem to be missing something because I expected mon_evt::evt_cfg
> of mbm_total_bytes and mbm_local_bytes to be initialized with a starting
> default. I missed where this is done in this series.

Its not done in this series. Will do in next revision.

> 
>> +		resctrl_update_assign(r, mevt->evtid, evt_cfg);
>> +	}
>> +
>> +unlock_out:
>> +	mutex_unlock(&rdtgroup_mutex);
>> +	cpus_read_unlock();
>> +
>> +	return ret ?: nbytes;
>> +}
>> +
>>   /* rdtgroup information files for one cache resource. */
>>   static struct rftype res_common_files[] = {
>>   	{
>> @@ -2056,9 +2173,10 @@ static struct rftype res_common_files[] = {
>>   	},
>>   	{
>>   		.name		= "event_filter",
>> -		.mode		= 0444,
>> +		.mode		= 0644,
>>   		.kf_ops		= &rdtgroup_kf_single_ops,
>>   		.seq_show	= event_filter_show,
>> +		.write		= event_filter_write,
>>   	},
>>   	{
>>   		.name		= "mbm_assign_mode",
> 
> Reinette
>