> Where did you see that PMC0 (PERSEL0/PERFCTR0) can only be programmed
> to count cpu cycles (i.e. cpu_clk_unhalted)? As far as I can tell from
> the documentation, the 4 counters are symetrical and can measure
> any event that the processor offers.
Linux NMI watchdog does that.
All other perfctr users are supposed to keep their fingers away
from the watchdog (it looks like oprofile doesn't but not for much
longer ...)
I think it's also a useful convention - RDTSC is becomming more and more
useless and you cannot expect user applications who just want to
measure some cycles to rely on ever changing instable or non existing
performance counter APIs.
> If you look at the perfmon x86-64 patch, you will see that under certain
> circumstances, we enable CR4.pce. The main motivation is to alloc reading
> counters at ring 3 with RDPMC. By default, CR4.pce must be cleared for
> security reasons (covert channel). Perfmon only allows RDPMC for
The same covert channel would exist with RDTSC so that argument is bogus.
-Andi
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
