Re: [Qemu-devel] [PATCH 00/25] q35 series take #1

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

On Sat, Sep 15, 2012 at 09:24:51AM +0900, Isaku Yamahata wrote:
> On Fri, Sep 14, 2012 at 03:01:55PM -0400, Jason Baron wrote:
> > On Sat, Sep 15, 2012 at 02:34:18AM +0900, Isaku Yamahata wrote:
> > > On Fri, Sep 14, 2012 at 11:23:29AM -0400, Jason Baron wrote:
> > > > On Sat, Sep 15, 2012 at 12:14:01AM +0900, Isaku Yamahata wrote:
> > > > > On Thu, Sep 13, 2012 at 04:12:34PM -0400, Jason Baron wrote:
> > > > > > 2) hotplug
> > > > > > I've added piix acpi style hotplug to ich9.
> > > > > 
> > > > > What's the point of this?
> > > > > Its design is ad-hoc and shpc/pcie hotplug are available.
> > > > 
> > > > The point was to get to feature parity with piix. I'm not sure how hard
> > > > pcie hotplug is to implement really. I was thinking that we could
> > > > replace the piix hotplug style with pcie hotplug, once that was
> > > > implemented...
> > > 
> > > shpc/pcie hotplug emulators are already available in qemu.
> > > hw/shpc.c, hw/pcie.c and hw/xio3130_downstream.c.
> > > 
> > > thanks,
> > > -- 
> > > yamahata
> > > 
> > 
> > ok, yes pcie hotplug seems to work :) I guess I got confused b/c I
> > thought devices would show up on the host bus. So the host bus in q35
> > simply doesn't support hotplug?
> 
> No, it doesn't.
> 
> 
> > Also, the way I'm doing hotplug is by specifying a 'bus=pcie.n' param.
> > Without the 'bus=pcie.n' param, i get: 
> > 
> > Bus 'pcie.0' does not support hotplugging
> > 
> > We probably then need to enhance 'device_add' to find a reasonable
> > default bus for the device on hotplug?
> 
> Yes.

By the way I would tread carefully before switching on
native hotplug support unconditionally in the BIOS.
For example, it has an
annoying two-second delay after device is added
and before it is used built into the spec that
might interfere with some uses.

As a minimum we might want to give users the ability to disable BIOS
native hotplug support.

> -- 
> yamahata