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Re: [Qemu-devel] virtio-rng and fd passing
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] virtio-rng and fd passing |
Date: |
Fri, 01 Mar 2013 17:14:01 -0600 |
User-agent: |
Notmuch/0.13.2+93~ged93d79 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Peter Krempa <address@hidden> writes:
> On 03/01/13 21:04, Anthony Liguori wrote:
>> Eric Blake <address@hidden> writes:
>>
>>> Stefan Berger and I discovered on IRC that virtio-rng is unable to
>>> support fd passing. We attempted:
>>>
>>> qemu-system-x86_64 ... -add-fd set=4,fd=34,opaque=RDONLY:/dev/urandom
>>> -object rng-random,id=rng0,filename=/dev/fdset/4 -device
>>> virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x6
>>
>> Why are you using th rng-random backend instead of the rng-egd backend?
>
> There are two issues with using the egd backend for unprepared devices:
>
> 1) The backend spits out "\x20\x40" commands(egd blocking entropy
> request for 0x40 bytes) so it really has to be used with some kind of
> EGD server implementation otherwise it might feed your /dev/random with
> predictable bytes if used directly.
Yes. That's the point.
>
> 2) performance of the egd backend is terrible as I've reported here
> https://bugzilla.redhat.com/show_bug.cgi?id=915381 (yes I'm aware that I
> probably should have filed a upstream bug too, but I was hoping Amit
> would do it in the process)
>
> On my machine I managed to do 0.2KiB/s with the egd backend both with
> using constant data as a high performance source, but also with a true
> random number generator (in the Raspberry pi SoC, sources 107KiB/s of
> entropy). The rng-random backend performs a bit better averaging
> 1.2MiB/s.
That's a bug that I wasn't aware of until you wrote this. I'll look
into it next week.
Regards,
Anthony Liguori
>
> Peter
- Re: [Qemu-devel] virtio-rng and fd passing, (continued)
- Re: [Qemu-devel] virtio-rng and fd passing, H. Peter Anvin, 2013/03/04
- Re: [Qemu-devel] virtio-rng and fd passing, Eric Blake, 2013/03/04
- Re: [Qemu-devel] virtio-rng and fd passing, Stefan Berger, 2013/03/01
- Re: [Qemu-devel] virtio-rng and fd passing, Anthony Liguori, 2013/03/01
- Re: [Qemu-devel] virtio-rng and fd passing, Stefan Berger, 2013/03/01
- Re: [Qemu-devel] virtio-rng and fd passing, Anthony Liguori, 2013/03/03
- Re: [Qemu-devel] virtio-rng and fd passing, Corey Bryant, 2013/03/04
- Re: [Qemu-devel] virtio-rng and fd passing, Daniel P. Berrange, 2013/03/04
- Re: [Qemu-devel] virtio-rng and fd passing, Corey Bryant, 2013/03/04
Re: [Qemu-devel] virtio-rng and fd passing, Peter Krempa, 2013/03/01
- Re: [Qemu-devel] virtio-rng and fd passing,
Anthony Liguori <=