On Monday 19 May 2008 19:10:49 Jeremy Fitzhardinge wrote: > Rusty Russell wrote: > > On Saturday 17 May 2008 17:47:01 Jeremy Fitzhardinge wrote: > >> But the host->guest protocol should include the number of bits estimated > >> entropy along with the bits themselves. > > > > If we go down that path, we have to come up with a way of feeding that > > information to guest userspace. Patches welcome. If we meanwhile assume > > entropy == #bits, it fits the current /dev/hwrng model, and we can add an > > entropy count later if we want to change that. > > Really? Wouldn't guest userspace just use /dev/random as usual, which I > think does have an ioctl to give that kind of information? And the > interfaces do allow things injecting entropy into the kernel pool to > provide entropy estimates along with the actual bits themselves. Unfortunately not. Hardware randomness devices export /dev/hwrng, and it's up to userspace to feed that into /dev/random (or not). That's usually done by rngd, which at least on my system, assumes 1 bit of entropy per bit of data from /dev/hwrng by default. I was a little surprised that this decision was exported to userspace, but if you're not prepared to unconditionally trust hw rngs, it makes sense to palm it off. We could write a boutique device for virtualization which *did* feed directly, but that would be a little gauche. Cheers, Rusty. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
