linux-kernel - Re: [PATCH v6 21/22] x86/resctrl: Introduce interface to list monitor states of all the groups

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Message-ID: <3d3acd15-3cf0-48eb-8b3b-53fdca1df7d2@amd.com>
Date: Fri, 16 Aug 2024 15:40:29 -0500
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
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Subject: Re: [PATCH v6 21/22] x86/resctrl: Introduce interface to list monitor
 states of all the groups

Hi James,

On 8/16/24 11:28, James Morse wrote:
> Hi Babu,
> 
> On 06/08/2024 23:00, Babu Moger wrote:
>> Provide the interface to list the monitor states of all the resctrl
>> groups in ABMC mode.
>>
>> Example:
>> $cat /sys/fs/resctrl/info/L3_MON/mbm_control
>>
>> List follows the following format:
>>
>> "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>>
>> Format for specific type of groups:
>>
>> - Default CTRL_MON group:
>>   "//<domain_id>=<flags>"
>>
>> - Non-default CTRL_MON group:
>>   "<CTRL_MON group>//<domain_id>=<flags>"
>>
>> - Child MON group of default CTRL_MON group:
>>   "/<MON group>/<domain_id>=<flags>"
>>
>> - Child MON group of non-default CTRL_MON group:
>>   "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>>
>> Flags can be one of the following:
>> t  MBM total event is enabled
>> l  MBM local event is enabled
>> tl Both total and local MBM events are enabled
>> _  None of the MBM events are enabled
> 
> 
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index d15fd1bde5f4..d7aadca5e4ab 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -965,6 +965,75 @@ static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
>>  	return 0;
>>  }
>>  
>> +static char *rdtgroup_mon_state_to_str(struct rdtgroup *rdtgrp,
>> +				       struct rdt_mon_domain *d, char *str)
>> +{
>> +	char *tmp = str;
>> +	int index;
>> +
>> +	/*
>> +	 * Query the monitor state for the domain.
>> +	 * Index 0 for evtid == QOS_L3_MBM_TOTAL_EVENT_ID
>> +	 * Index 1 for evtid == QOS_L3_MBM_LOCAL_EVENT_ID
>> +	 */
>> +	index = mon_event_config_index_get(QOS_L3_MBM_TOTAL_EVENT_ID);
>> +	if (rdtgrp->mon.cntr_id[index] != MON_CNTR_UNSET &&
>> +	    test_bit(rdtgrp->mon.cntr_id[index], d->mbm_cntr_map))
>> +		*tmp++ = 't';
>> +
>> +	index = mon_event_config_index_get(QOS_L3_MBM_LOCAL_EVENT_ID);
>> +	if (rdtgrp->mon.cntr_id[index] != MON_CNTR_UNSET &&
>> +	    test_bit(rdtgrp->mon.cntr_id[index], d->mbm_cntr_map))
>> +		*tmp++ = 'l';
>> +
>> +	if (tmp == str)
>> +		*tmp++ = '_';
>> +
>> +	*tmp = '\0';
>> +	return str;
>> +}
>> +
>> +static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
>> +				     struct seq_file *s, void *v)
>> +{
>> +	struct rdt_resource *r = of->kn->parent->priv;
> 
>> +	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> 
> This is filesystem code, once it moves to /fs/ you can't grab an architecture specific
> struct like this. (suggestion below).

Yes. Correct.  I don't need this. I will remove this.

> 
> 
>> +	struct rdt_mon_domain *dom;
>> +	struct rdtgroup *rdtg;
>> +	char str[10];
> 
> Shouldn't new commands that might fail start with rdt_last_cmd_clear()?

Yes. Correct.

> 
> 
>> +	if (!hw_res->mbm_cntr_assign_enabled) {
> 
> I think this should be wrapped up as:
> | resctrl_arch_mbm_cntr_assign_test(r)
> 
> as this flag is private to the architecture.

I can use resctrl_arch_get_abmc_enabled()

> 
> 
>> +		rdt_last_cmd_puts("ABMC feature is not enabled\n");
> 
> lockdep barks that you need to hold rdtgroup_mutex when calling rdt_last_cmd_puts() -
> otherwise this can run in parallel with another syscall.

Ok. Sure. Will fix it.

> 
>> +		return -EINVAL;
>> +	}
>> +
>> +	mutex_lock(&rdtgroup_mutex);
>> +
>> +	list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
>> +		struct rdtgroup *crg;
>> +
>> +		seq_printf(s, "%s//", rdtg->kn->name);
>> +
>> +		list_for_each_entry(dom, &r->mon_domains, hdr.list)
>> +			seq_printf(s, "%d=%s;", dom->hdr.id,
>> +				   rdtgroup_mon_state_to_str(rdtg, dom, str));
>> +		seq_putc(s, '\n');
>> +
>> +		list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
>> +				    mon.crdtgrp_list) {
>> +			seq_printf(s, "%s/%s/", rdtg->kn->name, crg->kn->name);
>> +
>> +			list_for_each_entry(dom, &r->mon_domains, hdr.list)
>> +				seq_printf(s, "%d=%s;", dom->hdr.id,
>> +					   rdtgroup_mon_state_to_str(crg, dom, str));
>> +			seq_putc(s, '\n');
>> +		}
>> +	}
>> +
>> +	mutex_unlock(&rdtgroup_mutex);
>> +	return 0;
>> +}
> 
> 
> Thanks,
> 
> James
> 
> 

-- 
Thanks
Babu Moger