Re: [Qemu-devel] [PATCH RFC 1/2] rng-egd: improve egd backend performance

[Anthony Liguori]

On Mon, Dec 16, 2013 at 8:36 AM, Amit Shah <address@hidden> wrote:
> On (Mon) 09 Dec 2013 [22:10:12], Amos Kong wrote:
>> Bugzilla: https://bugs.launchpad.net/qemu/+bug/1253563
>>
>> We have a requests queue to cache the random data, but the second
>> will come in when the first request is returned, so we always
>> only have one items in the queue. It effects the performance.
>>
>> This patch changes the IOthread to fill a fixed buffer with
>> random data from egd socket, request_entropy() will return
>> data to virtio queue if buffer has available data.
>>
>> (test with a fast source, disguised egd socket)
>>  # cat /dev/urandom | nc -l localhost 8003
>>  # qemu .. -chardev socket,host=localhost,port=8003,id=chr0 \
>>         -object rng-egd,chardev=chr0,id=rng0,buf_size=1024 \
>>         -device virtio-rng-pci,rng=rng0
>
> First thing I can think of is the egd protocol has a length field in
> the header, and if that isn't properly filled, the results are bound
> to be erratic.

The test is bogus.

egd is a protocol.  You can't just pipe /dev/urandom into it.

Regards,

Anthony Liguori

>
> I haven't been able to find a spec detailing the way egd API, perhaps
> Anthony knows how to best pass data to qemu via egd.
>
>                 Amit