linux-kernel - Re: [RFC PATCH 27/38] arm_mpam: resctrl: Add empty definitions for assorted resctrl functions

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Message-ID: <9b452304-27ea-4c38-8bf1-820cf4d2f0a7@arm.com>
Date: Tue, 9 Dec 2025 16:31:00 +0000
From: Ben Horgan <ben.horgan@....com>
To: James Morse <james.morse@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Cc: D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...nel.org>, Dave Martin <dave.martin@....com>,
 Koba Ko <kobak@...dia.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 fenghuay@...dia.com, baisheng.gao@...soc.com,
 Jonathan Cameron <jonathan.cameron@...wei.com>, Gavin Shan
 <gshan@...hat.com>, rohit.mathew@....com, reinette.chatre@...el.com,
 Punit Agrawal <punit.agrawal@....qualcomm.com>
Subject: Re: [RFC PATCH 27/38] arm_mpam: resctrl: Add empty definitions for
 assorted resctrl functions

Hi James,

On 12/5/25 21:58, James Morse wrote:
> A few resctrl features and hooks need to be provided, but aren't needed
> or supported on MPAM platforms.
> 
> resctrl has individual hooks to separately enable and disable the
> closid/partid and rmid/pmg context switching code. For MPAM this is all
> the same thing, as the value in struct task_struct is used to cache the
> value that should be written to hardware. arm64's context switching code
> is enabled once MPAM is usable, but doesn't touch the hardware unless
> the value has changed.
> 
> For now event configuration is not supported, and can be turned off
> by returning 'false' from resctrl_arch_is_evt_configurable().
> 
> Add this, and empty definitions for the other hooks.
> 
> Signed-off-by: James Morse <james.morse@....com>

The newly added io_alloc support means we need a couple more dummy
resctrl arch functions in here, resctrl_arch_io_alloc_enable() and
resctrl_arch_io_alloc_enabled().

Thanks,

Ben