Linux Virtualization - May 2008 - Virt RNG?

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.

	Jeff



[1] lkml&netdev thread: "[PATCH] drivers/net: remove network
drivers'
last few uses of IRQF_SAMPLE_RANDOM"

Jeff Garzik wrote:
> 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.
It was actually one of the first device types proposed for what would 
become virtio, but as far as I know there has been no work on such a 
device.  It certainly makes lots of sense.

    J

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

Dont know why it never hit mainline.

Christian

On Thu, May 15, 2008 at 02:48:53PM -0400, Jeff Garzik
wrote:
> Has anyone yet written a "hw" RNG module for virt, that reads the
host's
> random number pool?
UML has one, probably not usable as-is by anyone else right now...

    	     	      Jeff

-- 
Work email - jdike at linux dot intel dot com

On Friday 16 May 2008 04:48:53 Jeff Garzik wrote:
> 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, I prepared one earlier.  I was a little surprised to see that hwrng 
drivers don't contribute in any way to the entropy pool though, but now
reading the thread I find out about rngd (not installed on my Ubuntu system, 
but available at least).

One could argue that virtual rng should try to feed the kernel rng directly, 
with or without entropy credit.

Anyway, since there's interest, I'll drag virtio_rng from the bottom of
the
queue, apply Christian's fix (which I somehow missed before, sorry 
Christian), and re-post.

Thanks,
Rusty.