From: Josh Poimboeuf <jpoimboe@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH 7/9] TAA 7
Date: Thu, 24 Oct 2019 15:02:33 -0500 [thread overview]
Message-ID: <20191024200233.4alkoqepyltqua3l@treble> (raw)
In-Reply-To: <20191024195316.GI14115@zn.tnic>
On Thu, Oct 24, 2019 at 09:53:16PM +0200, speck for Borislav Petkov wrote:
> On Thu, Oct 24, 2019 at 08:20:42PM +0200, speck for Jiri Kosina wrote:
> > On Thu, 24 Oct 2019, speck for Borislav Petkov wrote:
> >
> > > "Disable TSX if the CPU is affected by the TSX Async Abort (TAA)
> > > vulnerability and microcode provides a special MSR - TSX_CTRL_MSR -
> > > which provides the required TSX control knobs. On MDS-affected parts
> > > where VERW takes care of the TAA vulnerability, that controlling MSR is
> > > not present and thus TSX cannot be disabled there."
> >
> > This is true if you ignore hyperthreading.
> >
> > On SMT systems, TSX disable is 100% complete mitigation, while VERW
> > clearing is not.
>
> So why is our default this then?
>
> static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW;
>
> and we only do the TAA_MITIGATION_TSX_DISABLED thing only if TSX has
> been disabled earlier?
>
> Because of those MDS_NO=0 machines which don't get the TSX_CTRL MSR so
> that TSX cannot be disabled there?
>
> Are some of those machines SMT?
>
> Because if so, we *must* disable SMT unconditionally to mitigate TAA
> completely there... methinks.
For the same reasons we kept SMT enabled for L1TF and MDS... We don't
want to break existing SMT workloads.
--
Josh
next prev parent reply other threads:[~2019-10-24 20:02 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-24 8:20 [MODERATED] [PATCH 0/9] TAA 0 Borislav Petkov
2019-10-23 8:45 ` [MODERATED] [PATCH 1/9] TAA 1 Pawan Gupta
2019-10-24 15:22 ` [MODERATED] " Josh Poimboeuf
2019-10-24 16:23 ` Borislav Petkov
2019-10-24 16:42 ` Josh Poimboeuf
2019-10-23 8:52 ` [MODERATED] [PATCH 2/9] TAA 2 Pawan Gupta
2019-10-23 9:01 ` [MODERATED] [PATCH 3/9] TAA 3 Pawan Gupta
2019-10-24 15:30 ` [MODERATED] " Josh Poimboeuf
2019-10-24 16:33 ` Borislav Petkov
2019-10-24 16:43 ` Josh Poimboeuf
2019-10-24 17:39 ` Andrew Cooper
2019-10-24 19:45 ` Borislav Petkov
2019-10-24 19:59 ` Josh Poimboeuf
2019-10-24 20:05 ` Borislav Petkov
2019-10-24 20:14 ` Josh Poimboeuf
2019-10-24 20:36 ` Borislav Petkov
2019-10-24 20:43 ` Andrew Cooper
2019-10-24 20:55 ` Borislav Petkov
2019-10-24 20:44 ` Josh Poimboeuf
2019-10-24 20:07 ` Andrew Cooper
2019-10-24 20:17 ` Borislav Petkov
2019-10-24 22:38 ` Andrew Cooper
2019-10-25 6:03 ` Pawan Gupta
2019-10-25 7:25 ` Borislav Petkov
2019-10-25 7:17 ` Borislav Petkov
2019-10-25 9:08 ` Andrew Cooper
2019-10-27 7:48 ` Borislav Petkov
2019-10-27 7:49 ` [MODERATED] [AUTOREPLY] [MODERATED] [AUTOREPLY] Automatic reply: " James, Hengameh M
2019-10-24 19:47 ` [MODERATED] " Pawan Gupta
2019-10-30 13:28 ` Greg KH
2019-10-30 14:48 ` [MODERATED] Re: ***UNCHECKED*** " Michal Hocko
2019-10-30 17:24 ` [MODERATED] " Pawan Gupta
2019-10-30 19:27 ` Greg KH
2019-10-30 19:44 ` [MODERATED] Re: ***UNCHECKED*** " Michal Hocko
2019-11-01 9:35 ` Greg KH
2019-11-01 13:15 ` [MODERATED] " Borislav Petkov
2019-11-01 14:33 ` Greg KH
2019-11-01 18:42 ` [MODERATED] Re: ***UNCHECKED*** " Michal Hocko
2019-10-23 9:30 ` [MODERATED] [PATCH 4/9] TAA 4 Pawan Gupta
2019-10-24 15:32 ` [MODERATED] " Josh Poimboeuf
2019-10-24 16:43 ` Borislav Petkov
2019-10-24 17:15 ` Josh Poimboeuf
2019-10-24 17:23 ` Pawan Gupta
2019-10-24 17:27 ` Pawan Gupta
2019-10-24 17:34 ` Josh Poimboeuf
2019-10-24 18:23 ` Andrew Cooper
2019-10-24 18:56 ` Josh Poimboeuf
2019-10-24 18:59 ` Josh Poimboeuf
2019-10-24 19:13 ` Andrew Cooper
2019-10-24 19:49 ` Josh Poimboeuf
2019-10-24 20:48 ` Andrew Cooper
2019-10-25 9:12 ` Andrew Cooper
2019-10-25 0:49 ` Pawan Gupta
2019-10-25 7:36 ` Borislav Petkov
2019-10-23 10:19 ` [MODERATED] [PATCH 5/9] TAA 5 Pawan Gupta
2019-10-24 18:30 ` [MODERATED] " Greg KH
2019-10-23 10:23 ` [MODERATED] [PATCH 6/9] TAA 6 Pawan Gupta
2019-10-23 10:28 ` [MODERATED] [PATCH 7/9] TAA 7 Pawan Gupta
2019-10-24 15:35 ` [MODERATED] " Josh Poimboeuf
2019-10-24 16:42 ` Borislav Petkov
2019-10-24 18:20 ` Jiri Kosina
2019-10-24 19:53 ` Borislav Petkov
2019-10-24 20:02 ` Josh Poimboeuf [this message]
2019-10-24 20:08 ` Borislav Petkov
2019-10-23 10:32 ` [MODERATED] [PATCH 8/9] TAA 8 Pawan Gupta
2019-10-24 16:03 ` [MODERATED] " Josh Poimboeuf
2019-10-24 17:35 ` Borislav Petkov
2019-10-24 18:11 ` Josh Poimboeuf
2019-10-24 18:55 ` Pawan Gupta
2019-10-25 8:04 ` Borislav Petkov
2019-10-23 10:35 ` [MODERATED] [PATCH 9/9] TAA 9 Michal Hocko
2019-10-24 16:10 ` [MODERATED] " Josh Poimboeuf
2019-10-24 16:58 ` Borislav Petkov
2019-10-25 10:47 ` [MODERATED] Re: ***UNCHECKED*** " Michal Hocko
2019-10-25 13:05 ` [MODERATED] " Josh Poimboeuf
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