Re: Virt RNG?

[Jeff Garzik]

Christian Borntraeger wrote:
> Am Donnerstag, 15. Mai 2008 schrieb Jeff Garzik:
> > Has anyone yet written a "hw" RNG module for virt, that reads the host's 
> > random number pool?
> >
> > All this talk[1] about IRQF_SAMPLE_RANDOM in network drivers reminds me 
> > that virt guest instances should be grabbing random numbers from the 
> > host, especially if the host has a hardware RNG.
>
> Yes, there was a drivers/char/hw_random/virtio-rng.c in Rusty's lguest 
> repository. 
> http://www.mail-archive.com/virtualization%40lists.linux-foundation.org/msg02902.html
>
> I have tested this driver with this fix
> https://lists.linux-foundation.org/pipermail/virtualization/2008-January/009737.html
> and it worked.

Nice!



> As it transfers only 4 byte per hypercall it is not mindblowingly fast, but I 
> guess it is fast enough.

A limitation of the hw-random API.  However, I'd say the virtio rng 
driver could (and should) buffer bigger chunks, say at least a 
cacheline's worth of data, to return via hw-random's 32-bit data request 
API.

	Jeff



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