linux-kernel - Re: [PATCH v4 15/39] x86/resctrl: Move monitor exit work to a resctrl exit call

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Message-ID: <e3c8709a-e9df-44fb-bb78-ede6fb44c758@arm.com>
Date: Mon, 30 Sep 2024 17:42:32 +0100
From: James Morse <james.morse@....com>
To: Reinette Chatre <reinette.chatre@...el.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 v4 15/39] x86/resctrl: Move monitor exit work to a resctrl
 exit call

Hi Reinette,

On 14/08/2024 05:01, Reinette Chatre wrote:
> On 8/2/24 10:28 AM, James Morse wrote:
>> rdt_put_mon_l3_config() is called via the architecture's
>> resctrl_arch_exit() call, and appears to free the rmid_ptrs[]
>> and closid_num_dirty_rmid[] arrays. In reality this code is marked
>> __exit, and is removed by the linker as resctrl can't be built
>> as a module.
>>
>> To separate the filesystem and architecture parts of resctrl,
>> this free()ing work needs to be triggered by the filesystem,
>> as these structures belong to the filesystem code.
>>
>> Rename rdt_put_mon_l3_config() resctrl_mon_resource_exit()
>> and call it from resctrl_exit(). The kfree() is currently
>> dependent on r->mon_capable.
>>
>> Signed-off-by: James Morse <james.morse@....com>
>> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
>> ---
>> Changes since v3:
>>   * Moved r->mon_capable check under the lock.
>>   * Dropped references to resctrl_mon_resource_init() from the commit message.
>>   * Fixed more resctrl typos,
>>
>> Changes since v2:
>>   * Dropped __exit as needed in the next patch.
> 
> Is this still relevant? It is unclear to me why __exit is dropped here.

resctrl_init() in the next patch wants to call resctrl_mon_resource_exit() as part of its
cleanup. This trips the mismatched section checks as the __exit code is discarded at link
time because you can't build resctrl as a module.

I'll opt for the churnier version that removes the exit markers in the next patch.


Thanks,

James