linux-kernel - Re: [PATCH] x86: make clflush a required feature on x86

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: <20080118141839.GA16738@one.firstfloor.org>
Date:	Fri, 18 Jan 2008 15:18:39 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Kyle McMartin <kyle@...artin.ca>,
	tglx@...utronix.de, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: make clflush a required feature on x86_64

On Fri, Jan 18, 2008 at 08:56:43AM -0500, H. Peter Anvin wrote:
> Andi Kleen wrote:
> >>Simulators can be fixed, 
> >
> >They could, but why? I don't know of a good reason to require CLFLUSH.
> 
> Well, simulators are generally expected to follow the architecture, not 
> vice versa.  I would tend to agree with the coupling that recent 
> versions of Bochs appeared to have made here -- I think we're unlikely 
> to see any processors with sse2 sans clflush, so keeping code branches 
> in which will never be executed seems like a bad idea in the long term. 

Here's another argument: Ingo just asked me to add a noclflush option
to the code. Guess what check that option will need? 

Besides compared to the cost of a flushing clflush the branches are absolutely 
in the noise.

-Andi
--
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/