Re: [Qemu-devel] [PATCH 1/3] Device isolation group infrastructure (v3)

[David Gibson]

On Thu, Feb 09, 2012 at 12:28:05PM +0100, Joerg Roedel wrote:
> On Thu, Feb 09, 2012 at 08:39:28AM +1100, Benjamin Herrenschmidt wrote:
> > On Wed, 2012-02-08 at 16:27 +0100, Joerg Roedel wrote:
> > > Again, device grouping is done by the IOMMU drivers, so this all
> > > belongs
> > > into the generic iommu-code rather than the driver core.
> > 
> > Except that there isn't really a "generic iommu code"... discovery,
> > initialization & matching of iommu vs. devices etc... that's all
> > implemented in the arch specific iommu code.
> 
> The whole point of moving the iommu drivers to drivers/iommu was to
> factor out common code. We are not where we want to be yet but the goal
> is to move more code to the generic part.
> 
> For the group-code this means that the generic code should iterate over
> all devices on a bus and build up group structures based on isolation
> information provided by the arch specific code.

And how exactly do you suggest it provide that information.  I really
can't see how an iommu driver would specify its isolation constraints
generally enough, except in the form of code and then we're back to
where we are now.

-- 
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