linux-kernel - Re: [PATCH v9 04/27] x86/resctrl: resctrl_exit() teardown resctrl but leave the mount point

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <669c32d0-384a-4224-87db-f8af551fd6d3@intel.com>
Date: Thu, 1 May 2025 10:03:20 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: 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>, Koba Ko <kobak@...dia.com>, Shanker
 Donthineni <sdonthineni@...dia.com>, <fenghuay@...dia.com>, Shaopeng Tan
	<tan.shaopeng@...fujitsu.com>, Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v9 04/27] x86/resctrl: resctrl_exit() teardown resctrl but
 leave the mount point

Hi James,

On 4/25/25 10:37 AM, James Morse wrote:
> @@ -4432,23 +4445,42 @@ static bool __exit resctrl_online_domains_exist(void)
>  	return false;
>  }
>  
> -/*
> +/**

Why make the switch to kernel-doc now? The benefit is not clear considering
resctrl_init() is not using kernel-doc.

>   * resctrl_exit() - Remove the resctrl filesystem and free resources.
>   *
> + * Called by the architecture code in response to a fatal error.
> + * Removes resctrl files and structures from kernfs to prevent further
> + * configuration.
> + *
>   * When called by the architecture code, all CPUs and resctrl domains must be
>   * offline. This ensures the limbo and overflow handlers are not scheduled to
>   * run, meaning the data structures they access can be freed by
>   * resctrl_mon_resource_exit().
> + *
> + * After this function has returned, the architecture code should return an

nit: "After this function has returned," -> "After resctrl_exit() returns, "

"should return an" -> "should return an error"?

> + * from all resctrl_arch_ functions that can do this.
> + * resctrl_arch_get_resource() must continue to return struct rdt_resources
> + * with the correct rid field to ensure the filesystem can be unmounted.

Is this to get through set_mba_sc() and the for_each_alloc_capable_rdt_resource(r)
loop in rdt_kill_sb() or is there something more subtle?

>   */
>  void __exit resctrl_exit(void)
>  {
>  	cpus_read_lock();
>  	WARN_ON_ONCE(resctrl_online_domains_exist());
> +
> +	mutex_lock(&rdtgroup_mutex);
> +	resctrl_fs_teardown();
> +	mutex_unlock(&rdtgroup_mutex);
> +
>  	cpus_read_unlock();
>  
>  	debugfs_remove_recursive(debugfs_resctrl);
> +	debugfs_resctrl = NULL;
>  	unregister_filesystem(&rdt_fs_type);
> -	sysfs_remove_mount_point(fs_kobj, "resctrl");
> +
> +	/*
> +	 * Do not remove the sysfs mount point added by resctrl_init() so that
> +	 * it can be used to umount resctrl.
> +	 */
>  
>  	resctrl_mon_resource_exit();
>  }

Looks good to me.

Thank you.

Reinette