Re: disable tsc with seccomp

From: Andi Kleen
Date: Mon Nov 21 2005 - 12:24:20 EST

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.

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