Re: Xen support for PCI-SIG I/O Virtualization

[Greg Law <glaw@solarflare.com>]

Hi Masroor,

Masroor Vettuparambil wrote:
> hi Greg, 
> 
> thanks for the comment.
> I have yet to go through ur work. Please provide a quick link.
> 
> I would like to know whether your proprietary mechanism supports virtual
> functions just like in IOV.
> If so, can you brief me on how this is accessed from the host and
> assigned to guest domains? 
> Infact I am more interested how this is happening in IOV method.

The framework is deliberately very generic.  Essentially it is just a 
way for netfront to have a plugin which can handle tx/rx of packets 
directly.  How this works (IOV, proprietary, whatever) is not the 
concern of the framework: you write netfront and netback plugins to 
implement it as required by your hardware.

The framework is not really intended to avoid you needing to write lots 
of code - it's not a "library".  Rather it's the minimum amount of 
infrastructure required so that VMs can be migrated between different 
hosts with different types of smart NICs (or no smart NICs).

No one has written an implementation of plugins that use IOV yet, but 
I'm pretty confident it will work without major changes.

As for the code, a good place to start is the definition of struct 
netfront_accel_hooks in linux/drivers/xen/netfront/netfront.h

The set of patches were posted to xen-devel by Kieran Mansley Fri, 18 
May 2007.  Sadly, I'm not sure what the change set number is, but you 
can get more info here: http://lwn.net/Articles/235124/

g

-- 
Greg Law          Solarflare Communications           +44 1223 518 040