From: Peter Zijlstra <peterz@infradead.org>
To: speck@linutronix.de
Subject: [MODERATED] Re: [patch V2 03/10] MDS basics+ 3
Date: Thu, 21 Feb 2019 10:27:00 +0100 [thread overview]
Message-ID: <20190221092700.GB32477@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1edb2eec-d17f-eefd-4c96-3c5c3eb69d09@citrix.com>
On Thu, Feb 21, 2019 at 02:12:19AM +0000, speck for Andrew Cooper wrote:
> On 20/02/2019 15:07, speck for Thomas Gleixner wrote:
> > +
> > + /*
> > + * Has to be memory form, don't modify to use a register. VERW
> > + * modifies ZF.
>
> I don't understand why everyone is so concerned about VERW modifying
> ZF. Its not as if this fact is relevant anywhere that the mitigation is
> liable to be used.
>
> > + */
> > + asm volatile("verw %[ds]" : : "i" (0), [ds] "m" (ds) : "cc");
>
> The "i" (0) isn't referenced in the assembly, and can be dropped.
>
> On a tangent, have GCC or Clang made any indication that they're going
> to stop assuming that all asm() statements clobber flags, and start
> making the "cc" clobber necessary on x86 targets?
Not as far as I know, but that doesn't mean we shouldn't use it
properly.
next prev parent reply other threads:[~2019-02-21 9:27 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-20 15:07 [patch V2 00/10] MDS basics+ 0 Thomas Gleixner
2019-02-20 15:07 ` [patch V2 01/10] MDS basics+ 1 Thomas Gleixner
2019-02-20 16:27 ` [MODERATED] " Borislav Petkov
2019-02-20 16:46 ` Greg KH
2019-02-20 15:07 ` [patch V2 02/10] MDS basics+ 2 Thomas Gleixner
2019-02-20 16:47 ` [MODERATED] " Borislav Petkov
2019-02-20 16:48 ` Greg KH
2019-02-20 15:07 ` [patch V2 03/10] MDS basics+ 3 Thomas Gleixner
2019-02-20 16:54 ` [MODERATED] " mark gross
2019-02-20 16:57 ` Thomas Gleixner
2019-02-20 18:08 ` [MODERATED] " mark gross
2019-02-20 21:40 ` Thomas Gleixner
2019-02-20 17:14 ` [MODERATED] " Borislav Petkov
2019-02-20 21:31 ` Thomas Gleixner
2019-02-21 2:12 ` [MODERATED] " Andrew Cooper
2019-02-21 9:27 ` Peter Zijlstra [this message]
2019-02-21 9:33 ` [MODERATED] " Borislav Petkov
2019-02-21 10:04 ` Thomas Gleixner
2019-02-21 10:18 ` [MODERATED] Re: " Borislav Petkov
2019-02-20 15:07 ` [patch V2 04/10] MDS basics+ 4 Thomas Gleixner
2019-02-20 16:52 ` [MODERATED] " Greg KH
2019-02-20 17:10 ` mark gross
2019-02-21 19:26 ` [MODERATED] Encrypted Message Tim Chen
2019-02-21 20:32 ` Thomas Gleixner
2019-02-21 21:07 ` [MODERATED] " Jiri Kosina
2019-02-20 18:43 ` [MODERATED] Re: [patch V2 04/10] MDS basics+ 4 Borislav Petkov
2019-02-20 19:26 ` Jiri Kosina
2019-02-20 21:42 ` Thomas Gleixner
2019-02-20 15:07 ` [patch V2 05/10] MDS basics+ 5 Thomas Gleixner
2019-02-20 20:05 ` [MODERATED] " Borislav Petkov
2019-02-21 2:24 ` Andrew Cooper
2019-02-21 10:36 ` Thomas Gleixner
2019-02-21 11:22 ` Thomas Gleixner
2019-02-21 11:51 ` [MODERATED] Attack Surface [Was [patch V2 05/10] MDS basics+ 5] Andrew Cooper
2019-02-21 18:41 ` Thomas Gleixner
2019-02-20 15:07 ` [patch V2 06/10] MDS basics+ 6 Thomas Gleixner
2019-02-21 10:18 ` [MODERATED] " Borislav Petkov
2019-02-20 15:08 ` [patch V2 07/10] MDS basics+ 7 Thomas Gleixner
2019-02-21 12:47 ` [MODERATED] " Borislav Petkov
2019-02-21 13:48 ` Thomas Gleixner
2019-02-20 15:08 ` [patch V2 08/10] MDS basics+ 8 Thomas Gleixner
2019-02-21 14:04 ` [MODERATED] " Borislav Petkov
2019-02-21 14:11 ` Thomas Gleixner
2019-02-20 15:08 ` [patch V2 09/10] MDS basics+ 9 Thomas Gleixner
2019-02-20 16:21 ` [MODERATED] " Peter Zijlstra
2019-02-20 22:32 ` Thomas Gleixner
2019-02-20 22:50 ` [MODERATED] " Jiri Kosina
2019-02-20 23:22 ` Thomas Gleixner
2019-02-21 11:04 ` [MODERATED] " Peter Zijlstra
2019-02-21 11:50 ` Peter Zijlstra
2019-02-21 14:18 ` Borislav Petkov
2019-02-21 18:00 ` Kees Cook
2019-02-21 19:46 ` Thomas Gleixner
2019-02-21 20:56 ` Thomas Gleixner
2019-02-20 15:08 ` [patch V2 10/10] MDS basics+ 10 Thomas Gleixner
2019-02-22 16:05 ` [MODERATED] Re: [patch V2 00/10] MDS basics+ 0 mark gross
2019-02-22 17:12 ` Thomas Gleixner
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