Date: Mon, 21 Nov 2005 18:24:44 +0100
From: Andi Kleen <ak@suse.de>
To: Andrea Arcangeli <andrea@cpushare.com>
Cc: Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>
Subject: Re: disable tsc with seccomp
Message-ID: <20051121172444.GB20775@brahms.suse.de>
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On Mon, Nov 21, 2005 at 06:16:16PM +0100, Andrea Arcangeli wrote:
> On Mon, Nov 21, 2005 at 06:05:17PM +0100, Andi Kleen wrote:
> > On Mon, Nov 21, 2005 at 05:43:49PM +0100, Andrea Arcangeli wrote:
> > > Since there was no feedback to my last post, I assume you agree, so
> > > please backout the tsc disable so then I can plug the performane counter
> > > disable on top of it (at zero additional runtime cost).
> > 
> > Sorry I don't agree.
> 
> You've the config option, turn that off on your systems, what's the
> problem with that?
> 
> Or does this mean I need to ship kernels myself with covert channels
> made mathematically impossible with seccomp enabled? I'd rather avoid

I don't believe theoretical, unlikely to be usable in any way
covert channels are a justification to make fast paths slower. 
That's independent of CONFIG options.

And in addition your change doesn't even close that channel
in theory.

-Andi
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