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From: Jiri Kosina <jikos@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>,
	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>, Waiman Long <longman9394@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Willy Tarreau <w@1wt.eu>
Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes
Date: Mon, 19 Nov 2018 14:49:36 +0100 (CET)	[thread overview]
Message-ID: <nycvar.YFH.7.76.1811191438290.21108@cbobk.fhfr.pm> (raw)
In-Reply-To: <alpine.DEB.2.21.1811191433100.1537@nanos.tec.linutronix.de>

On Mon, 19 Nov 2018, Thomas Gleixner wrote:

> > On Sat, 17 Nov 2018, Jiri Kosina wrote:
> 
> > Subject: [PATCH] x86/speculation: enforce STIBP for SECCOMP tasks in lite mode
> > 
> > If 'lite' mode of app2app protection from spectre_v2 is selected on
> > kernel command-line, we are currently applying STIBP protection to
> > non-dumpable tasks, and tasks that have explicitly requested such
> > protection via
> > 
> > 	prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0);
> > 
> > Let's extend this to cover also SECCOMP tasks (analogically to how we
> > apply SSBD protection).
> 
> Right. And SSBD does not fiddle with dumpable.
> 
> Willy had concerns about the (ab)use of dumpable so I'm holding off on that
> bit for now.

Yeah. IBPB implementation used to check the dumpability of tasks during 
rescheduling, but that went away later.

I still think that ideally that 'app2app' setting would toggle how IBPB is 
being used as well, something along the lines:

lite:
	- STIBP for the ones marked via prctl() and SECCOMP with the TIF_ 
	  flag
	- ibpb_needed() returning true for the same

strict:
	- STIBP: as currently implemented
	- ibpb_needed() returning always true

off:
	- neither STIBP nor IBPB applied ever

That's give us also some % of performance lost via IBPB back.

Makes sense?

Thanks,

-- 
Jiri Kosina
SUSE Labs


  reply	other threads:[~2018-11-19 13:49 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-17  1:53 [Patch v5 00/16] Provide task property based options to enable Spectre v2 userspace-userspace protection Tim Chen
2018-11-17  1:53 ` [Patch v5 01/16] x86/speculation: Clean up spectre_v2_parse_cmdline() Tim Chen
2018-11-17  1:53 ` [Patch v5 02/16] x86/speculation: Remove unnecessary ret variable in cpu_show_common() Tim Chen
2018-11-17  1:53 ` [Patch v5 03/16] x86/speculation: Reorganize cpu_show_common() Tim Chen
2018-11-17  1:53 ` [Patch v5 04/16] x86/speculation: Add X86_FEATURE_USE_IBRS_ENHANCED Tim Chen
2018-11-17  1:53 ` [Patch v5 05/16] x86/speculation: Disable STIBP when enhanced IBRS is in use Tim Chen
2018-11-17  1:53 ` [Patch v5 06/16] x86/speculation: Rename SSBD update functions Tim Chen
2018-11-17  1:53 ` [Patch v5 07/16] x86/speculation: Reorganize speculation control MSRs update Tim Chen
2018-11-17  1:53 ` [Patch v5 08/16] smt: Create cpu_smt_enabled static key for SMT specific code Tim Chen
2018-11-19 12:58   ` Thomas Gleixner
2018-11-19 20:50     ` Tim Chen
2018-11-19 14:57   ` Peter Zijlstra
2018-11-19 18:08     ` Tim Chen
2018-11-19 19:03       ` Thomas Gleixner
2018-11-19 19:25         ` Tim Chen
2018-11-17  1:53 ` [Patch v5 09/16] x86/smt: Convert cpu_smt_control check to cpu_smt_enabled static key Tim Chen
2018-11-19 12:48   ` Thomas Gleixner
2018-11-19 12:59     ` Thomas Gleixner
2018-11-17  1:53 ` [Patch v5 10/16] x86/speculation: Turn on or off STIBP according to a task's TIF_STIBP Tim Chen
2018-11-17  1:53 ` [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes Tim Chen
2018-11-17  9:47   ` Jiri Kosina
2018-11-18 22:59     ` Jiri Kosina
2018-11-19 13:36       ` Thomas Gleixner
2018-11-19 13:49         ` Jiri Kosina [this message]
2018-11-19 13:51           ` Thomas Gleixner
2018-11-19 14:00             ` Jiri Kosina
2018-11-19 18:31               ` Tim Chen
2018-11-19 19:32           ` Andrea Arcangeli
2018-11-19 19:39             ` Jiri Kosina
2018-11-19 21:40               ` Andrea Arcangeli
2018-11-19 21:33             ` Dave Hansen
2018-11-19 23:16               ` Andrea Arcangeli
2018-11-19 23:25                 ` Dave Hansen
2018-11-19 23:45                   ` Andrea Arcangeli
2018-11-20  0:22                 ` Thomas Gleixner
2018-11-19 13:32   ` Thomas Gleixner
2018-11-20  0:08     ` Tim Chen
2018-11-20  0:30       ` Thomas Gleixner
2018-11-20  1:14         ` Tim Chen
2018-11-20  1:17         ` Andi Kleen
2018-11-19 15:00   ` Thomas Gleixner
2018-11-19 18:27     ` Tim Chen
2018-11-19 18:31       ` Jiri Kosina
2018-11-19 20:21   ` Thomas Gleixner
2018-11-19 22:44     ` Tim Chen
2018-11-19 20:46   ` Thomas Gleixner
2018-11-19 20:55     ` Jiri Kosina
2018-11-19 21:12       ` Thomas Gleixner
2018-11-19 22:48       ` Tim Chen
2018-11-19 23:01         ` Thomas Gleixner
2018-11-19 23:23           ` Jiri Kosina
2018-11-20  0:00             ` Thomas Gleixner
2018-11-20  0:24               ` Tim Chen
2018-11-19 23:39           ` Dave Hansen
2018-11-19 23:49             ` Jiri Kosina
2018-11-20  0:02               ` Thomas Gleixner
2018-11-17  1:53 ` [Patch v5 12/16] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Tim Chen
2018-11-17  9:53   ` Jiri Kosina
2018-11-19 18:29     ` Tim Chen
2018-11-17  1:53 ` [Patch v5 13/16] security: Update speculation restriction of a process when modifying its dumpability Tim Chen
2018-11-17  1:53 ` [Patch v5 14/16] x86/speculation: Use STIBP to restrict speculation on non-dumpable task Tim Chen
2018-11-17  1:53 ` [Patch v5 15/16] x86/speculation: Update comment on TIF_SSBD Tim Chen
2018-11-17  1:53 ` [Patch v5 16/16] x86: Group thread info flags by functionality Tim Chen
2018-11-17  9:34 ` [Patch v5 00/16] Provide task property based options to enable Spectre v2 userspace-userspace protection Jiri Kosina

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