linux-kernel - Re: Specific support for Intel Atom architecture

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: <20090512150408.GH19296@one.firstfloor.org>
Date:	Tue, 12 May 2009 17:04:08 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Ulrich Drepper <drepper@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Tobias Doerffel <tobias.doerffel@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Specific support for Intel Atom architecture

On Tue, May 12, 2009 at 07:20:14AM -0700, Ulrich Drepper wrote:
> On Mon, May 4, 2009 at 12:22 AM, Andi Kleen <andi@...stfloor.org> wrote:
> > This should be obsolete anyways, you can just uses CORE2. They have compatible ISAs.
> 
> Only correct if you don't plan to use the movbe instruction.  The
> kernel would be the one place where I can imagine this to make sense.

The problem is that you can't express the situations where
movbe is better than bswap (you need both and the old and the new
value) in inline assembler in a way that gcc decides automatically.

I also doubt there are many (any?) situations in the kernel where
the destruction of the old register is a problem in the kernel;
e.g. the network stack normally doesn't care.

My understanding is that movbe is really mainly useful for 
some special situations where you run a emulator/jit for 
a BE ISA, but that's not something the kernel does.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
--
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/