Re: [PATCH/RFC 7/9] Virtual network guest device driver

Dor Laor
2007-05-13T20:31:32Z

Subject: Re: [kvm-devel] [PATCH/RFC 7/9] Virtual network guest device
>driver
>
>On Sun, May 13, 2007 at 11:49:14AM -0500, Anthony Liguori wrote:
>> Dor Laor wrote:
>> > Furthermore,
>> >
>> >> the plan is to completely rearchitect the netback/netfront
>> >> protocol for the next Xen release (this effort is referred to
>> >> netchannel2).
>> >>
>> >
>> > But isn't Jeremy Fitzhardinge is pushing big patch queue into the
>> > kernel?
>> >
>>
>> Yes, but it's not in the kernel yet and there's no guarantee it'll
>> get there in time for KVM's consumption.
>
>On the other hand, there's strong interest in having unified virtual
>drivers. Given that the Xen drivers are out there, have been submitted
>and have been reasonably optimized, there will be some resistance to
>putting in "yet another" set of PV drivers. Also, the contentious
>merge point as I understand it is xenbus needing review, rather than
>the drivers themselves which are in pretty good shape.

Moreover, it's not that it is too complex to write set of back/front
ends, it just it's already written and optimized down to the bit.
Our current implementation has all the regular bells and whistles
(rings, delayed notifications, napi) it is simper than Xen's but it
lacks further optimizations and tso/scatter gather.
If we even use the NetChannel2 we should enjoy from smart NIC features
too.
It's more tempting and fun to continue to support our implementation but
it's righter to reuse code.
Nevertheless, we'll be happy to hear and discuss what others are
thinking.

If the current Xen code fail to hit the kernel, then it would be even
easier for us - we'll just rip off all the Xen wrapping, the grant
tables and the flipping would go away leaving clean optimized network
code.
Regards,
Dor.