linux-kernel - Re: [PATCH v10 22/24] x86/resctrl: Update assignments on event configuration changes

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Message-ID: <5e1471a0-3484-4273-9be7-94d084d2cc4d@intel.com>
Date: Thu, 19 Dec 2024 19:12:27 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<tony.luck@...el.com>, <peternewman@...gle.com>
CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
	<paulmck@...nel.org>, <akpm@...ux-foundation.org>, <thuth@...hat.com>,
	<rostedt@...dmis.org>, <xiongwei.song@...driver.com>,
	<pawan.kumar.gupta@...ux.intel.com>, <daniel.sneddon@...ux.intel.com>,
	<jpoimboe@...nel.org>, <perry.yuan@....com>, <andipan.das@....com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <seanjc@...gle.com>,
	<xin3.li@...el.com>, <andrew.cooper3@...rix.com>, <ebiggers@...gle.com>,
	<mario.limonciello@....com>, <james.morse@....com>,
	<tan.shaopeng@...itsu.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <maciej.wieczor-retman@...el.com>,
	<eranian@...gle.com>
Subject: Re: [PATCH v10 22/24] x86/resctrl: Update assignments on event
 configuration changes

Hi Babu,

On 12/12/24 12:15 PM, Babu Moger wrote:
> Resctrl provides option to configure events by writing to the interfaces
> /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config or
> /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config when BMEC (Bandwidth
> Monitoring Event Configuration) is supported.
> 
> Whenever the event configuration is updated, MBM assignments must be
> revised across all monitor groups within the impacted domains.

This needs imperative tone description of what this patch does. 

 
...

> @@ -1825,6 +1825,54 @@ static int mbm_local_bytes_config_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +/*
> + * Review the cntr_cfg domain configuration. If a matching assignment is found,
> + * update the counter assignment accordingly. This is within the IPI Context,

This "Review the cntr_cfg domain configuration. If a matching assignment is found,"
is too vague for me to make sense of what it is trying to do. Can this be made more specific?

> + * so call resctrl_abmc_config_one_amd directly.
> + */
> +static void resctrl_arch_update_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				     enum resctrl_event_id evtid, u32 val)
> +{
> +	struct cntr_config config;
> +	struct rdtgroup *rdtgrp;
> +	struct mbm_state *m;
> +	u32 cntr_id;
> +
> +	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
> +		rdtgrp = d->cntr_cfg[cntr_id].rdtgrp;
> +		if (rdtgrp && d->cntr_cfg[cntr_id].evtid == evtid) {
> +			memset(&config, 0, sizeof(struct cntr_config));
> +			config.r = r;
> +			config.d = d;
> +			config.evtid = evtid;
> +			config.rmid = rdtgrp->mon.rmid;
> +			config.closid = rdtgrp->closid;
> +			config.cntr_id = cntr_id;
> +			config.val = val;
> +			config.assign = 1;
> +
> +			resctrl_abmc_config_one_amd(&config);
> +
> +			m = get_mbm_state(d, rdtgrp->closid, rdtgrp->mon.rmid, evtid);
> +			if (m)
> +				memset(m, 0, sizeof(struct mbm_state));
> +		}
> +	}
> +}
> +
> +static void resctrl_mon_event_config_set(void *info)
> +{
> +	struct mon_config_info *mon_info = info;
> +	struct rdt_mon_domain *d = mon_info->d;
> +	struct rdt_resource *r = mon_info->r;
> +
> +	resctrl_arch_mon_event_config_set(d, mon_info->evtid, mon_info->mon_config);
> +
> +	/* Check if assignments needs to be updated */
> +	if (resctrl_arch_mbm_cntr_assign_enabled(r))
> +		resctrl_arch_update_cntr(r, d, mon_info->evtid,
> +					 mon_info->mon_config);
> +}
>  
>  static void mbm_config_write_domain(struct rdt_resource *r,
>  				    struct rdt_mon_domain *d, u32 evtid, u32 val)
> @@ -1840,6 +1888,7 @@ static void mbm_config_write_domain(struct rdt_resource *r,
>  	if (config_val == INVALID_CONFIG_VALUE || config_val == val)
>  		return;
>  
> +	mon_info.r = r;
>  	mon_info.d = d;
>  	mon_info.evtid = evtid;
>  	mon_info.mon_config = val;
> @@ -1851,7 +1900,7 @@ static void mbm_config_write_domain(struct rdt_resource *r,
>  	 * on one CPU is observed by all the CPUs in the domain.
>  	 */
>  	smp_call_function_any(&d->hdr.cpu_mask,
> -			      resctrl_arch_mon_event_config_set,
> +			      resctrl_mon_event_config_set,
>  			      &mon_info, 1);
>  
>  	/*

Reinette