Re: [PATCH v5 06/18] vfio-user: add HotplugHandler for remote machine

[Stefan Hajnoczi]

On Wed, Jan 26, 2022 at 03:20:35PM +0000, Jag Raman wrote:
> 
> 
> > On Jan 26, 2022, at 4:35 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > 
> > On Tue, Jan 25, 2022 at 06:12:48PM +0000, Jag Raman wrote:
> >> 
> >> 
> >>> On Jan 25, 2022, at 5:32 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> >>> 
> >>> On Wed, Jan 19, 2022 at 04:41:55PM -0500, Jagannathan Raman wrote:
> >>>> Allow hotplugging of PCI(e) devices to remote machine
> >>>> 
> >>>> Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
> >>>> Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
> >>>> Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
> >>>> ---
> >>>> hw/remote/machine.c | 29 +++++++++++++++++++++++++++++
> >>>> 1 file changed, 29 insertions(+)
> >>> 
> >>> Why is this code necessary? I expected the default hotplug behavior to
> >> 
> >> I just discovered that TYPE_REMOTE_MACHINE wasn't setting up a hotplug
> >> handler for the root PCI bus.
> >> 
> >> Looks like, some of the machines don’t support hotplugging PCI devices. I 
> >> see
> >> that the ‘pc’ machine does support hotplug, whereas ‘q35’ does not.
> > 
> > Hotplug is definitely possible with q35. I'm not familiar with the
> > hotplug code though so I don't know how exactly that works for q35.
> 
> I was referring to the root PCI bus, other buses in Q35 probably support
> hotplug. Please see error message below:
> 
> QEMU 6.2.50 monitor - type 'help' for more information
> (qemu) device_add lsi53c895a,id=lsi2
> Error: Bus 'pcie.0' does not support hotplugging

Yes, I think that's because it's PCIe and not PCI.

Stefan

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