Re: [Qemu-devel] kvm PCI assignment & VFIO ramblings

[David Gibson]

On Wed, Aug 24, 2011 at 01:03:32PM +0200, Roedel, Joerg wrote:
> On Wed, Aug 24, 2011 at 05:33:00AM -0400, David Gibson wrote:
> > On Wed, Aug 24, 2011 at 11:14:26AM +0200, Roedel, Joerg wrote:
> 
> > > I don't see a reason to make this meta-grouping static. It would harm
> > > flexibility on x86. I think it makes things easier on power but there
> > > are options on that platform to get the dynamic solution too.
> > 
> > I think several people are misreading what Ben means by "static".  I
> > would prefer to say 'persistent', in that the meta-groups lifetime is
> > not tied to an fd, but they can be freely created, altered and removed
> > during runtime.
> 
> Even if it can be altered at runtime, from a usability perspective it is
> certainly the best to handle these groups directly in qemu. Or are there
> strong reasons to do it somewhere else?

Funny, Ben and I think usability demands it be the other way around.

If the meta-groups are transient - that is lifetime tied to an fd -
then any program that wants to use meta-groups *must* know the
interfaces for creating one, whatever they are.

But if they're persistent, the admin can use other tools to create the
meta-group then just hand it to a program to use, since the interfaces
for _using_ a meta-group are identical to those for an atomic group.

This doesn't preclude a program from being meta-group aware, and
creating its own if it wants to, of course.  My guess is that qemu
would not want to build its own meta-groups, but libvirt probably
would.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson