Hi Arjan, On Mon, May 11, 2009 at 01:22:01PM +0200, Arjan Koers wrote: > Harald Welte wrote: > >> How can multiple RNGs in current dual-processor setups and in the future > >> multicore Nano be handled? > > > > That's actually a good question. I'll probably forward that to the CPU > > division and see what they come up with. I would assume you just run the > > initialization on every CPU, and that's it. > > It would probably have to be setup the same on all CPUs (enabled on all / > disabled on all), because the code might execute on any CPU. yes, but I don't really consider this a practical problem. I think there is no practical case where half of the CPUs want a hardware RNG, and half of them don't. If somebody really has that kind of special need, he can probably patch his kernel himself. > > Now the more interesting question is: how can the hw_random framework deal > > with it? As far as I remember, it can only select one out of N available > > concurrent providers of hardware randomness. correct? > > I don't know, but it would be nice if it could use PadLock functionality on > multiple CPUs at the same time for increased speed. I'm not so sure if that really makes sense just to increase throughput of a single workload / work item. However, for multiple concurrent threads, of course each thread on each CPU should be able to use the padlock instructions for AES / PHE / RNG. And if you enable the feature on all CPU's during the respective module_init(), it should simply work afterwards. > > This is due to the fact that the MSR itself does no longer exist on the Nano. > > It only exists on C3 to C7 silicon. > > Thanks for the information. Do you happen to know what changed for the other > MSRs that are used for ACE, PowerSaver, ...? I unfortunately don't [yet] but I'll inquire. > Since the Nano RNG can't be configured, the patch could be changed to > something like this: yes, thanks. looks fine to me. > If it's possible for a Nano to have the cpuid rng flag set and the > rng_en flag unset, init_c3 in arch/x86/kernel/cpu/centaur.c may have > to be changed too. This seems very unlikely to me, because there would > be no way to enable the RNG then. I'll re-confirm this with the CPU R&D, too. Regards, -- - Harald Welte <HaraldWelte@xxxxxxxxxxx> http://linux.via.com.tw/ ============================================================================ VIA Open Source Liaison -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
