linux-kernel - Re: [PATCH v1 28/31] x86/resctrl: Drop __init/_

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Date: Mon, 8 Apr 2024 20:32:36 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: Fenghua Yu <fenghua.yu@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, H Peter Anvin
	<hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	<shameerali.kolothum.thodi@...wei.com>, 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@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>, Dave
 Martin <dave.martin@....com>
Subject: Re: [PATCH v1 28/31] x86/resctrl: Drop __init/__exit on assorted
 symbols

Hi James,

On 3/21/2024 9:51 AM, James Morse wrote:
> Because ARM's MPAM controls are probed using MMIO, resctrl can't be
> initialised until enough CPUs are online to have determined the
> system-wide supported num_closid. Arm64 also supports 'late onlined
> secondaries', where only a subset of CPUs are online during boot.
> 
> These two combine to mean the MPAM driver may not be able to initialise
> resctrl until user-space has brought 'enough' CPUs online.
> 
> To allow MPAM to initialise resctrl after __init text has been free'd,
> remove all the __init markings from resctrl.
> 
> The existing __exit markings cause these functions to be removed by the
> linker as it has never been possible to build resctrl as a module. MPAM
> has an error interrupt which causes the driver to reset and disable
> itself. Remove the __exit markings to allow the MPAM driver to tear down
> resctrl when an error occurs.

Obviously for the reasons you state this code has never been exercised.
Were you able to test this error interrupt flow yet?

Reinette