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Date: Fri, 29 Aug 2025 13:26:49 +0100
From: Dave Martin <Dave.Martin@arm.com>
To: James Morse <james.morse@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Subject: Re: [PATCH] arm_mpam: Relax num_rmids parameter advertised to
 userspace
Message-ID: <aLGciannXznRgwsb@e133380.arm.com>
References: <20250820131621.54983-1-Dave.Martin@arm.com>
 <58eae4c3-51b3-48ad-b077-aefdff969119@arm.com>
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In-Reply-To: <58eae4c3-51b3-48ad-b077-aefdff969119@arm.com>

Hi James,

On Wed, Aug 27, 2025 at 06:16:00PM +0100, James Morse wrote:
> Hi Dave,
> 
> On 20/08/2025 14:15, Dave Martin wrote:
> > On MPAM systems, monitoring groups are identified in the hardware by a
> > (PARTID, PMG) pair.  Two monitoring group identifiers are the same only
> > if the PARTIDs and PMGs both match.  This means that the number of
> > monitoring groups that can be created in each control group is the same
> > as the number of distinct PMG values supported by the hardware.  The
> > number of monitoring groups that exist in other control groups at the
> > same time makes no difference to this.
> > 
> > Currently, the MPAM driver takes the cautious approach and always
> > num_rmids = 1.
> > 
> > Relax this limit, by advertising the number of distinct PMG values
> > supported by the hardware.
> > 
> > Code/Data Prioritization (CDP) makes no difference, since although this
> > doubles the number of (PARTID, PMG) pairs available to a control group,
> > each monitoring group now consumes two pairs instead of one.
> 
> Thanks, I've picked this up. It may get squashed into the patch that adds these lines
> before going upstream...
> 
> 
> Thanks,
> 
> James

Thanks for picking this up.

Will that be in the next snapshot?

Cheers
---Dave
>