Re: [Qemu-devel] [patch 2/2] qemu: PCI device, disk and host network hot-add / hot-remove

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, Feb 09, 2009 at 08:41:39AM +0000, Daniel P. Berrange wrote:
> On Sun, Feb 08, 2009 at 03:28:45PM -0200, Marcelo Tosatti wrote:
> > On Sun, Feb 08, 2009 at 12:08:34PM +0200, Avi Kivity wrote:
> > > Marcelo Tosatti wrote:
> > >> Add monitor command to hot-add PCI devices (nic and storage).
> > >>     Syntax is:
> > >>     pci_add pci_addr=[[<domain>:]<bus>:]<slot> nic|storage params
> > >>     It returns the domain, bus and slot for the newly added device on 
> > >> success
> > >
> > > Instead of returning something, how about
> > >
> > >  pci_add pci_addr=...,name=blah
> > >
> > > and then
> > >
> > >  pci_del blah
> > >
> > > 'info pci' could also output the name so that it could be associated  
> > > with the bus address.
> > 
> > Sure that can be done. Like an alias. So you identify <domain,bus,slot>
> > with a name. I can see it simplifies direct management of hotplug on the
> > monitor.
> 
> Also bear in mind that we need the ability to hot unplug devices which
> were specified on the command line argv. For these we currently have
> neither the pci <domain,bus,slot>, nor are given any 'name'. 

Any reason you can't discover <domain,bus,slot> from "info pci" ?
(domain/bus are always zero at the moment).

> Markus has previously suggested allowing <domain,bus,slot> to be
> specified on the cli which would let us manually assign & use that
> info for unplug.

> A device type specific unique naming would be useful too though. In
> changeset r6220,  Mark McLoughlin provided the ability to give every
> single NIC a unique name. I'd like to be able to use that name for
> unplug. 

The NIC identifiers are not specific to PCI. So if you specify a
non-PCI nic with the cli, you should not expect "pci_del name" to work.
Now I see where you're getting at with the private discussion around
"dev_add/dev_add".

Ok, simply adding a PCI specific identifier can be messy (since it will
clash with net identifier, for example).

So what is needed is, perhaps, a unique identifier
across all devices in the system? (hum, QEMUDevice from
http://bellard.org/qemu/patches/qemu-config2.diff).

> For disks, meanwhile we generally know the logic bus,unit,index info as
> provided to -drive / pci_add disk, which can be used to unplug.
> 
> So, I'd suggest that pci_del allow either a <domain,bus,slot>

It does.

> or some form of unique name, or device type specific unique
> identifier. Ideally so we can still just as easily use unplug for
> devices added on the cli, as for those added via the monitor.

info pci should work.

Thanks.