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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [patch V5 09/14] MDS basics 9
Date: Fri, 1 Mar 2019 08:04:15 -0600	[thread overview]
Message-ID: <20190301140415.pjv7qjellvqrlbw5@treble> (raw)
In-Reply-To: <20190227152037.818666801@linutronix.de>

On Wed, Feb 27, 2019 at 04:09:48PM +0100, speck for Thomas Gleixner wrote:
> Subject: [patch V5 09/14] x86/speculation/mds: Conditionally clear CPU buffers on idle entry
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> Add a static key which controls the invocation of the CPU buffer clear
> mechanism on idle entry. This is independent of other MDS mitigations
> because the idle entry invocation to mitigate the potential leakage due to
> store buffer repartitioning is only necessary on SMT systems.
> 
> Add the actual invocations to the different halt/mwait variants which
> covers all usage sites. mwaitx is not patched as it's not available on
> Intel CPUs.
> 
> The buffer clear is only invoked before entering the C-State to prevent
> that stale data from the idling CPU is spilled to the Hyper-Thread sibling
> after the Store buffer got repartitioned and all entries are available to
> the non idle sibling.

Andrea brought up a good question privately -- this patch mitigates
MSBDS for HT, but HT will still be susceptible to the other two MDS
issues.  So what's the point?  It seems this patch only protects people
who don't care about MDS in the first place.

-- 
Josh

  reply	other threads:[~2019-03-01 14:04 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-27 15:09 [patch V5 00/14] MDS basics 0 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 01/14] MDS basics 1 Thomas Gleixner
2019-02-28 13:08   ` Thomas Gleixner
2019-02-27 15:09 ` [patch V5 02/14] MDS basics 2 Thomas Gleixner
2019-02-28 13:55   ` [MODERATED] " Josh Poimboeuf
2019-02-28 14:09     ` Thomas Gleixner
2019-02-28 20:23       ` [MODERATED] " Josh Poimboeuf
2019-03-01 16:04         ` Thomas Gleixner
2019-02-27 15:09 ` [patch V5 03/14] MDS basics 3 Thomas Gleixner
2019-02-27 16:34   ` [MODERATED] " Greg KH
2019-02-27 15:09 ` [patch V5 04/14] MDS basics 4 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 05/14] MDS basics 5 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 06/14] MDS basics 6 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 07/14] MDS basics 7 Thomas Gleixner
2019-02-27 17:07   ` [MODERATED] " Greg KH
2019-02-27 15:09 ` [patch V5 08/14] MDS basics 8 Thomas Gleixner
2019-02-28  8:11   ` [MODERATED] " Greg KH
2019-02-27 15:09 ` [patch V5 09/14] MDS basics 9 Thomas Gleixner
2019-03-01 14:04   ` Josh Poimboeuf [this message]
2019-03-01 16:03     ` Thomas Gleixner
2019-03-01 16:40       ` [MODERATED] " Josh Poimboeuf
2019-03-01 18:39         ` Josh Poimboeuf
2019-03-01 19:15           ` Thomas Gleixner
2019-03-01 22:38             ` [MODERATED] " Andrea Arcangeli
2019-03-01 22:58               ` Thomas Gleixner
2019-03-02 19:22                 ` [MODERATED] Re: [SPAM] " Dave Hansen
2019-03-02 20:39                   ` Thomas Gleixner
2019-02-27 15:09 ` [patch V5 10/14] MDS basics 10 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 11/14] MDS basics 11 Thomas Gleixner
2019-02-27 15:09 ` [patch V5 12/14] MDS basics 12 Thomas Gleixner
2019-03-01 22:00   ` [MODERATED] " mark gross
2019-02-27 15:09 ` [patch V5 13/14] MDS basics 13 Thomas Gleixner
2019-03-01 22:04   ` [MODERATED] " mark gross
2019-02-27 15:09 ` [patch V5 14/14] MDS basics 14 Thomas Gleixner
2019-02-27 17:49   ` Thomas Gleixner
2019-02-27 16:26 ` [MODERATED] Re: [patch V5 00/14] MDS basics 0 Linus Torvalds
2019-02-27 17:51   ` Thomas Gleixner
2019-02-27 18:13     ` Thomas Gleixner
2019-02-27 19:50       ` [MODERATED] " Linus Torvalds
2019-02-27 20:05         ` Thomas Gleixner
2019-02-27 21:04 ` Thomas Gleixner
2019-02-28  1:04   ` [MODERATED] " Josh Poimboeuf
2019-02-27 23:06 ` mark gross
2019-02-28  6:58   ` Thomas Gleixner

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