Re: [RFC] libxl hotplug / unplug emulated devices

[Wei Liu <wei.liu2@citrix.com>]

On Fri, May 20, 2016 at 05:38:44PM +0100, Ian Jackson wrote:
> Wei Liu writes ("[RFC] libxl hotplug / unplug emulated devices"):
> > Recently I got a report on xen-users@ about xl network-attach not
> > working for HVM guest.
> > 
> > I try to use
> >   xl network-attach jessie-hvm 'bridge=xenbr0'
> > and vif-bridge script complains that it can't add vifXX-emu to bridge.
> > 
> > The underlying issue is that the vif spec provided defaults to
> > emulated nic, but libxl only populates a pv nic but doesn't call out
> > via QMP to QEMU to populate one. Note that this issue not only affects
> > nic device but essentially all device types.
> 
> Is it really sensible to offer emulated nic hotplug ?  That'd be
> presented to the guest as pci hotplug, I guess ?

Suppose you have a Windows guest doesn't have PV driver? Or any other
OSes that have PCI drivers with hotplug support but not Xen drivers?

For the second question, yes, more or less the same if you're talking
about libxl side implementation. It's going to call some QMP commands.

> 
> > I also experimented with block device:
> >   xl block-attach jessie-hvm 'phy:/dev/DATA/disk,hdb,w'
> > and it succeed, only pv disk is populated though.
> 
> That's what I would have expected.
> 
> Maybe the fix should be that xl network-attach should default hotplug
> nics to pv only.
> 

I certainly am fine with this.

Wei.

> Ian.

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