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SubjectRe: Virt RNG?
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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