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From: Thomas Gleixner <tglx@linutronix.de>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Jiri Kosina <jikos@kernel.org>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Casey Schaufler <casey.schaufler@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Jon Masters <jcm@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [Patch v3 07/13] x86/process Add arch_set_dumpable
Date: Fri, 19 Oct 2018 21:12:48 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1810192100130.1651@nanos.tec.linutronix.de> (raw)
In-Reply-To: <c8bb3ea2-d060-5cad-1544-ae5ff5f8fd3b@linux.intel.com>

On Thu, 18 Oct 2018, Tim Chen wrote:
> On 10/18/2018 06:28 AM, Thomas Gleixner wrote:
> > 
> > So now the obvious question. set_dumpable() operates on tsk->mm. i.e. it's
> > a process wide operation. But arch_set_dumpable() operates on the task
> > itself. What about the other tasks of that process?
> 
> I missed this part.
> 
> Fixing this is tricky as I don't see an easy way to
> reverse map mm back to all tasks that use the same mm
> to update their STIBP flags.

task is known and handed in to the function. So why do you want to reverse
map mm?

for_each_thread(task, ...) is what you want. The only thing to verify is
whether you can lock the tasks sighand lock there. And then it's enough to
set/clear the TIF bit and let it take effect at the next context switch.

Thanks,

	tglx





  reply	other threads:[~2018-10-19 19:13 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-17 17:59 [Patch v3 00/13] Provide process property based options to enable Spectre v2 userspace-userspace protection Tim Chen
2018-10-17 17:59 ` [Patch v3 01/13] x86/speculation: Clean up spectre_v2_parse_cmdline Tim Chen
2018-10-18 12:43   ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 02/13] x86/speculation: Remove unnecessary ret variable in cpu_show_common Tim Chen
2018-10-18 12:46   ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 03/13] x86/speculation: Add static key for Enhanced IBRS Tim Chen
2018-10-18 12:50   ` Thomas Gleixner
2018-10-26 16:58   ` Waiman Long
2018-10-26 18:15     ` Tim Chen
2018-10-28  9:32       ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 04/13] x86/speculation: Disable STIBP when enhanced IBRS is in use Tim Chen
2018-10-18 12:58   ` Thomas Gleixner
2018-10-26 17:00   ` Waiman Long
2018-10-26 18:18     ` Tim Chen
2018-10-26 18:29       ` Tim Chen
2018-10-17 17:59 ` [Patch v3 05/13] x86/smt: Create cpu_smt_enabled static key for SMT specific code Tim Chen
2018-10-18 13:03   ` Thomas Gleixner
2018-10-19  7:51   ` Peter Zijlstra
2018-10-17 17:59 ` [Patch v3 06/13] mm: Pass task instead of task->mm as argument to set_dumpable Tim Chen
2018-10-18 13:22   ` Thomas Gleixner
2018-10-19 20:02   ` Peter Zijlstra
2018-10-17 17:59 ` [Patch v3 07/13] x86/process Add arch_set_dumpable Tim Chen
2018-10-18 13:28   ` Thomas Gleixner
2018-10-18 18:46     ` Tim Chen
2018-10-19 19:12       ` Thomas Gleixner [this message]
2018-10-19 20:16         ` Thomas Gleixner
2018-10-22 23:55           ` Tim Chen
2018-10-17 17:59 ` [Patch v3 08/13] x86/speculation: Rename SSBD update functions Tim Chen
2018-10-18 13:37   ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 09/13] x86/speculation: Reorganize SPEC_CTRL MSR update Tim Chen
2018-10-18 13:47   ` Thomas Gleixner
2018-10-26 17:21   ` Waiman Long
2018-10-26 18:25     ` Tim Chen
2018-10-17 17:59 ` [Patch v3 10/13] x86/speculation: Add per thread STIBP flag Tim Chen
2018-10-18 13:53   ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 11/13] x86/speculation: Add Spectre v2 lite app to app protection mode Tim Chen
2018-10-18 15:12   ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 12/13] x86/speculation: Protect non-dumpable processes against Spectre v2 attack Tim Chen
2018-10-18 15:17   ` Thomas Gleixner
2018-10-26 17:46   ` Waiman Long
2018-10-26 18:10     ` Tim Chen
2018-10-17 17:59 ` [Patch v3 13/13] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Tim Chen
2018-10-17 19:12   ` Randy Dunlap
2018-10-18 15:31   ` Thomas Gleixner
2018-10-19  7:57 ` [Patch v3 00/13] Provide process property based options to enable Spectre v2 userspace-userspace protection Peter Zijlstra
2018-10-19 16:43   ` Tim Chen
2018-10-19 18:38     ` Peter Zijlstra

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