linux-kernel - Re: [PATCH v2 22/29] arm_mpam: Add helpers to allocate monitors

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Message-ID: <2e5d3b5e-0d76-4594-8a65-9baa635cfcd8@arm.com>
Date: Mon, 6 Oct 2025 15:57:16 +0100
From: James Morse <james.morse@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-acpi@...r.kernel.org,
 D Scott Phillips OS <scott@...amperecomputing.com>,
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 David Hildenbrand <david@...hat.com>, Dave Martin <dave.martin@....com>,
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 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Danilo Krummrich <dakr@...nel.org>, Ben Horgan <ben.horgan@....com>
Subject: Re: [PATCH v2 22/29] arm_mpam: Add helpers to allocate monitors

Hi Jonathan,

On 12/09/2025 14:11, Jonathan Cameron wrote:
> On Wed, 10 Sep 2025 20:43:02 +0000
> James Morse <james.morse@....com> wrote:
> 
>> MPAM's MSC support a number of monitors, each of which supports
>> bandwidth counters, or cache-storage-utilisation counters. To use
>> a counter, a monitor needs to be configured. Add helpers to allocate
>> and free CSU or MBWU monitors.
>>
>> Signed-off-by: James Morse <james.morse@....com>
>> Reviewed-by: Ben Horgan <ben.horgan@....com>
> 
> One minor requested change inline that will probably otherwise get picked
> up by someone's cleanup script
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

Thanks!


>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>> index 326ba9114d70..81c4c2bfea3d 100644
>> --- a/drivers/resctrl/mpam_internal.h
>> +++ b/drivers/resctrl/mpam_internal.h

>> +static inline int mpam_alloc_mbwu_mon(struct mpam_class *class)
>> +{
>> +	struct mpam_props *cprops = &class->props;
>> +
>> +	if (!mpam_has_feature(mpam_feat_msmon_mbwu, cprops))
>> +		return -EOPNOTSUPP;
>> +
>> +	return ida_alloc_range(&class->ida_mbwu_mon, 0,
>> +			       cprops->num_mbwu_mon - 1, GFP_KERNEL);
> 
> ida_alloc_max() - which is just a wrapper that sets the minimum to 0
> but none the less perhaps conveys things slightly better.

Sure - I didn't spot that when I did this.


Thanks,

James