Re: [PATCH][HVM] pass-through PCI device hotplug support

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Jan 25, 2008 at 09:31:34AM +0800, Zhai, Edwin wrote:
> On Thu, Jan 24, 2008 at 06:06:56PM +0000, Daniel P. Berrange wrote:
> > > 
> > > "xm dpci-remove" hot remove the specified vtd device by the ID, like:
> > > xm dpci-remove EdwinHVMDomainVtd 0
> > > 
> > > "xm dpci-insert" hot add a new vtd device, like '03:00.0':
> > > xm dpci-insert EdwinHVMDomainVtd 3 0 0
> > 
> > IMHO we shouldn't have a 'd' on the front of the command names. VT-d is a 
> > vendor specific implementation whose nomenculture doesn't need to be exposed
> 
> 'd' means directly assigned device, which is generic including VT-d and other 
> pass-through device..
> 
> Anyway, it's not so important.
> 
> > to users. In addition the existing block & network hotplug commands use
> > 'attach' and 'detach' for their command names. So for sake of consistency
> > I'd recommend command names of:
> > 
> >   pci-list
> >   pci-attach
> >   pci-detach
> 
> I had the same idea at the beginning, but change mind due to some concerns:
> 
> xxx-attach/detach are used for _PV_ driver, but dpci is not the case.
> If pci PV driver support hotplug in future, we get a complicated code path to 
> handle both PV and dpci's hotplug.

I don't buy that argument. You can still just have completely separate
codepaths inside XenD if you really need to - just switch on different
impls in the main RPC dispatcher...

 def pci_attach()
    if dom.is_hvm():
       pci_attach_hvm()
    else
       pci_attach_pv()

Every part of Xen where we expose the user to a difference between HVM
vs PV is a point of pain. We should ensure that use of HVM & PV is as 
near as possible, identical from a user's view.

> So do we have plan to support PCI PV driver hotplug? If no, we can use 
> pci-attach/detach.

>From the user's point of view they are attaching & detaching PCI devices, 
and they should not have to use separate commands to do the same operation
for PV vs HVM.

Regards,
Dan.
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