linux-kernel - Re: Intel Memory Ordering White Paper

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: <200709080632.05389.nickpiggin@yahoo.com.au>
Date:	Sat, 8 Sep 2007 06:32:05 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andi Kleen <ak@...e.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Intel Memory Ordering White Paper

On Saturday 08 September 2007 20:19, Andi Kleen wrote:
> On Friday 07 September 2007 21:57:35 Nick Piggin wrote:
> > > > Anyway, the lfence should be able to go away without so much trouble.
> > >
> > > You mean sfence? lfence in rmb is definitely needed.
> >
> > I mean lfence in smp_rmb().
>
> One point of rmb is to stop speculative loads and I don't think we
> can get that without lfence.

smp_rmb() should not need to do anything because loads are done
in order anyway. Both AMD and Intel have committed to this now.

The important point is that they *appear* to be done in order. AFAIK,
the CPUs can still do speculative and out of order loads, but throw
out the results if they could be wrong.
-
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/