From: Thomas Gleixner <tglx@linutronix.de>
To: Jiri Kosina <jikos@kernel.org>
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>,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes
Date: Tue, 20 Nov 2018 01:00:18 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1811200047470.1669@nanos.tec.linutronix.de> (raw)
In-Reply-To: <nycvar.YFH.7.76.1811200021000.21108@cbobk.fhfr.pm>
On Tue, 20 Nov 2018, Jiri Kosina wrote:
> On Tue, 20 Nov 2018, Thomas Gleixner wrote:
>
> > What? IBPB makes tons of sense even without STIBP.
>
> On non-SMT, yes. But this patchset ties those two the other (sensible) way
> around AFAICS ("STIBP iff (IBPB && SMT)").
Errm. No.
The patches disable IBPB if STIBP is not available and that has absolutely
nothing to do with SMT simply because the static key controlling IBPB is
only flipped on when both IBPB and STIBP are available.
For SMT=off STIBP is pointless, but IBPB still makes a lot of sense.
That's a change which is neither documented nor correct.
Thanks,
tglx
next prev parent reply other threads:[~2018-11-20 0:00 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
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 [this message]
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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