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Date: Thu, 11 Apr 2024 15:26:31 +0100
From: Dave Martin <Dave.Martin@arm.com>
To: Reinette Chatre <reinette.chatre@intel.com>
Cc: James Morse <james.morse@arm.com>, x86@kernel.org,
	linux-kernel@vger.kernel.org, Fenghua Yu <fenghua.yu@intel.com>,
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Subject: Re: [PATCH v1 28/31] x86/resctrl: Drop __init/__exit on assorted
 symbols
Message-ID: <ZhfzF8L6w1pgJJ1r@e133380.arm.com>
References: <20240321165106.31602-1-james.morse@arm.com>
 <20240321165106.31602-29-james.morse@arm.com>
 <c27c7813-5744-4363-bb7b-f9fbe80fd549@intel.com>
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In-Reply-To: <c27c7813-5744-4363-bb7b-f9fbe80fd549@intel.com>

On Mon, Apr 08, 2024 at 08:32:36PM -0700, Reinette Chatre wrote:
> 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
> 

I think this will have to wait for James to respond.

There is code to tear down resctrl in response to an MPAM error interrupt,
but I don't know how it has been exercised so far (if at all).

https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/tree/drivers/platform/mpam/mpam_devices.c?h=mpam/snapshot/v6.7-rc2#n1940


Cheers
---Dave