[PATCH 0/6] qemu: Fix cdrom as SCSI hostdev via -blockdev

[Peter Krempa]

On Sun, Oct 18, 2020 at 14:34:16 +0200, daggs wrote:
> Greetings All,
> 
> > Sent: Thursday, October 15, 2020 at 6:25 PM
> > From: "Peter Krempa" <pkrempa at redhat.com>
> > To: libvir-list at redhat.com
> > Cc: "daggs" <daggs at gmx.com>
> > Subject: [PATCH 0/6] qemu: Fix cdrom as SCSI hostdev via -blockdev
> >
> > -drive detects whether a device is a cdrom automatically but we need to
> > use 'host_cdrom' when using blockdev explicitly. Fix the hostdev code
> > which was recently converted to -blockdev.
> >
> > Warning:
> >
> > I _don't_ have a box with a CDROM handy so this code is not tested in action!
> >
> > Peter Krempa (6):
> >   qemuProcessCreatePretendCmd: Split up preparation and command building
> >   qemu: hostdev: Prepare definition bits in qemuDomainPrepareHostdev
> >   qemu: Prepare hostdev data which depends on the host state separately
> >   qemuxml2argvmock: Remove mocking of 'virSCSIDeviceGetSgName'
> >   qemu: Detect whether a SCSI hostdev is a cdrom
> >   qemu: Add test cases for 'host_cdrom' blockdev backend via <disk>
> 
> I've tested the bellow on libvirt 6.8.0, I wasn't able to get it to work, with the same entry as the example, e.g.:
>     <hostdev mode='subsystem' type='scsi' managed='yes'>
>       <source>
>         <adapter name='cdrom'/>

This is purely for tests, to force a cdrom since we can't probe the
host. Using it for a VM will fail.

>         <address bus='0' target='0' unit='0'/>
>       </source>
>       <readonly/>
>       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>     </hostdev>
> I get this error:
> error: XML error: SCSI host device doesn't support managed mode.
> 
> if I mark the managed as no (like other pci pass-through devices I have in the vm), I get this error:
> error: internal error: Cannot parse adapter 'cdrom'

Yup, this is expected, you need to use a real 'adapterN' here.