cvs commit: src/sys/amd64/amd64 mp_machdep.csrc/sys/amd64/include cpufunc.h src/sys/i386/i386 mp_machdep.c src/sys/i386/include cpufunc.h

Peter Jeremy peterjeremy at
Mon May 16 01:00:41 PDT 2005

On Sun, May 15, 2005 at 01:13:56PM -0700, Nate Lawson wrote:
>My point was that FreeBSD (like most general-purpose OS) has many timing 
>channels that are comparably as effective for an attacker as HTT. 

If you take the bandwidth of the timing channel into account, I don't
believe there are any other timing channels that come anywhere near the
HTT attack.  Maybe Colin has a better idea of what other timing channels
exist and how they compare to HTT.

>Disabling HTT does not significantly reduce an attacker's likelihood of 
>success since they can just use another timing channel.  However, it 
>does disable a useful feature.  Are we going to disable SMP next?

How useful is HTT on FreeBSD?  FreeBSD does not have a HTT-aware
scheduler at present and I don't believe there are even any plans to
make either scheduler HTT-aware.  Without this, you only gain a benefit
if you are running fairly specific workloads.


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