linux-kernel - Re: [patch 2/2] x86 amd fix cmpxchg read acquire barrier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090423131941.GA11261@Krystal>
Date:	Thu, 23 Apr 2009 09:19:42 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, mark.langsdorf@....com,
	arekm@...en.pl, "H. Peter Anvin" <hpa@...or.com>,
	Andi Kleen <andi@...stfloor.org>, Avi Kivity <avi@...ranet.com>
Subject: Re: [patch 2/2] x86 amd fix cmpxchg read acquire barrier

* Ingo Molnar (mingo@...e.hu) wrote:
> 
> * Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:
> 
> > " // Opteron Rev E has a bug in which on very rare occasions a locked
> >   // instruction doesn't act as a read-acquire barrier if followed by a
> >   // non-locked read-modify-write instruction.  Rev F has this bug in 
> >   // pre-release versions, but not in versions released to customers,
> >   // so we test only for Rev E, which is family 15, model 32..63 inclusive.
> 
> Dunno. The fix looks a bit intrusive (emits a NOP even on good 
> CPUs). Also, the text above says "not in versions released to 
> customers".
> 
> So unless there's an official erratum or reports in the field (not 
> from early prototype systems shipped to developers) i'd not rush to 
> apply it, just yet.
> 

Actually, Operon Rev E has this bug in the field (family 15, model
32..64). Rev F only had the bug in pre-releases.

But yes, it's bad that it drags so many code additions to something as
critical as cmpxchg. I start to think it might be better to just
disallow bringing up more than one CPU on these machines.

Mathieu

> 	Ingo

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/