linux-kernel - Re: [PATCH v2 39/45] arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl

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Message-ID: <5b7a66e2-7310-4770-bb7c-c7d7993cd6fe@arm.com>
Date: Thu, 8 Jan 2026 14:53:37 +0000
From: Ben Horgan <ben.horgan@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
 baolin.wang@...ux.alibaba.com, carl@...amperecomputing.com,
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Subject: Re: [PATCH v2 39/45] arm_mpam: resctrl: Call resctrl_init() on
 platforms that can support resctrl

Hi Jonathan,

On 1/6/26 14:58, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 18:11:41 +0000
> Ben Horgan <ben.horgan@....com> wrote:
> 
>> From: James Morse <james.morse@....com>
>>
>> Now that MPAM links against resctrl, call resctrl_init() to register the
>> filesystem and setup resctrl's structures.
>>
>> Signed-off-by: James Morse <james.morse@....com>
>> Signed-off-by: Ben Horgan <ben.horgan@....com>
> 
> Just minor suggestions inline.  I'm not sure the for loop macros
> are worth doing but that particular pair of loops feel awfully familiar
> at this point, so maybe. 
> 
> Either way..
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
>  
>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
>> index 059148c38a38..bbb12b5dfd8c 100644
>> --- a/drivers/resctrl/mpam_resctrl.c
>> +++ b/drivers/resctrl/mpam_resctrl.c
> 
>> @@ -1840,11 +1861,70 @@ int mpam_resctrl_setup(void)
>>  		pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
>>  	}
>>  
>> -	/* TODO: call resctrl_init() */
>> +	err = resctrl_init();
>> +	if (!err)
>> +		WRITE_ONCE(resctrl_enabled, true);
> 
> Trivial but I'd prefer the error path out of line.
> 
> 	if (err)
> 		return err;
> 
> 	WRITE_ONCE(resctrl_enabled, true);
> 	
> 	return 0;

Ok, updated.

>>  
>>  	return err;
>>  }
> 
>> +
>> +/*
>> + * The driver is detaching an MSC from this class, if resctrl was using it,
>> + * pull on resctrl_exit().
>> + */
>> +void mpam_resctrl_teardown_class(struct mpam_class *class)
>> +{
>> +	int i;
>> +	struct mpam_resctrl_res *res;
>> +	struct mpam_resctrl_mon *mon;
>> +
>> +	might_sleep();
>> +
>> +	for (i = 0; i < RDT_NUM_RESOURCES; i++) {
> There are enough iterators over these that I wonder
> if it is worth some macros.
>  
> 	for_each_mpam_resctrl_control(res) {
> 	}
> and
> 	for_each_mpam_resctrl_counter(mon) {
> 	}

The index is often needed too so I changed to helpers that include it too:
for_each_mpam_resctrl_control(res, rid) and
for_each_mpam_resctrl_mon(mon, eventid).

> 
> 
>> +		res = &mpam_resctrl_controls[i];
>> +		if (res->class == class) {
>> +			res->class = NULL;
>> +			break;
>> +		}
>> +	}
>> +	for (i = 0; i < QOS_NUM_EVENTS; i++) {
>> +		mon = &mpam_resctrl_counters[i];
>> +		if (mon->class == class) {
>> +			mon->class = NULL;
>> +
>> +			mpam_resctrl_teardown_mon(mon, class);
>> +
>> +			break;
>> +		}
>> +	}
>> +}
>> +
>>  static int __init __cacheinfo_ready(void)
>>  {
>>  	cacheinfo_ready = true;
> 

Thanks,

Ben