Re: [Xen-devel] [PATCH 3/4] libxl: only allow guests with a device model to use cd-{eject/insert}

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Wei Liu writes ("Re: [PATCH 3/4] libxl: only allow guests with a device model 
to use cd-{eject/insert}"):
> On Fri, Apr 08, 2016 at 04:17:55PM +0200, Roger Pau Monné wrote:
> > It's specific to guests with a device model (those are the only ones that 
> > can have an emulated CDROM device), and the only guests that can have a 
> > device model are HVM (although not all of them).
> 
> Remind me again: how does PV guest CDROM work? ISTR it will also go
> through this function? My memory is vague though...

I think an "empty" cdrom drive is represented to the guest as a
0-length block device.

There seem to be varying views as to whether insert/remove is supposed
to involve a vbd state teardown/restart, or just a capacity change.

From what I think Roger said, Linux blkback doesn't spot changes to
params (obviously - it looks for physdev) and AIUI needs to be
prodded.

Ian.

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