Re: [Qemu-devel] [PATCH v2 21/21] q35: add acpi-based pci hotplug.

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 11, 2012 at 10:21:22AM -0400, Jason Baron wrote:
> On Thu, Oct 11, 2012 at 12:57:06PM +0200, Michael S. Tsirkin wrote:
> > On Mon, Oct 08, 2012 at 11:30:39PM -0400, Jason Baron wrote:
> > > From: Jason Baron <jbaron@redhat.com>
> > > 
> > > Add piix style acpi hotplug to q35.
> > > 
> > > Signed-off-by: Jason Baron <jbaron@redhat.com>
> > 
> > Something I don't understand here: this only handles hotplug
> > of devices behind the root, no?
> > Don't we need support for hotplug/hot remove of devices behind
> > bridges?
> > 
> 
> Yes, this only handles acpi hotplug of devices behind the root. I'm
> trying to reach minimal set of q35 patches that we can build upon. I
> think that this patch gives us at least the same functionality as piix
> does. (Plus there is pcie hotplug).
> 
> As you know, I have a proof of concept patch series providing a second
> level of hotplug behind bridges. Unfortunately, it was based on the
> static acpi tables, before Paolo made the hotplug table generation
> dynamic. So it needs quite a bit of re-work. But I know that it should
> work :)
> 
> Thanks,
> 
> -Jason

Yes. Reason I ask is because q35 is adding bridges by default now.
Would it be possible to only add them if requested on command line by user
instead? I realize some guests expect devices at specific slots
but this does not apply to bridges I think?

It would also be nice to add comments explaining why
specific slots were selected e.g. /* BSD XYZ fails to boot unless ahci is at alow 2 */
etc.

Also - will adding this code now mean that when adding bridges
we'll need to add compatibility code in bios/qemu in the future?

-- 
MST