Re: Hyper-Threading Vulnerability

[Arjan van de Ven]

On Sat, 2005-05-14 at 15:21 -0400, Lee Revell wrote:
> On Sat, 2005-05-14 at 20:01 +0200, Arjan van de Ven wrote:
> > On Sat, 2005-05-14 at 13:56 -0400, Lee Revell wrote:
> > > On Sat, 2005-05-14 at 18:44 +0200, Arjan van de Ven wrote:
> > > > then JACK is terminally broken if it doesn't have a fallback for non-
> > > > rdtsc cpus. 
> > > 
> > > It does have a fallback, but the selection is done at compile time.  It
> > > uses rdtsc for all x86 CPUs except pre-i586 SMP systems.
> > > 
> > > Maybe we should check at runtime,
> > 
> > it's probably a sign that JACK isn't used on SMP systems much, at least
> > not on the bigger systems (like IBM's x440's) where the tsc *will*
> > differ wildly between cpus...
> 
> Correct.  The only bug reports we have seen related to the use of the
> TSC is due to CPU frequency scaling.  The fix is to not use it - people
> who want to use their PC as a DSP for audio probably don't want their
> processor slowing down anyway. 

it's a matter of time (my estimate is a year or two) before processors
get variable frequencies based on temperature targets etc...
and then rdtsc is really useless for this kind of thing..


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