[libvirt] [PATCH v2] domain_conf: skip boot order check of CD-ROM or floppy device when change-media

[Chen Hanxiao]

At 2018-01-11 21:36:29, "Ján Tomko" <jtomko at redhat.com> wrote:
>On Thu, Jan 11, 2018 at 06:16:37PM +0800, Chen Hanxiao wrote:
>>From: Chen Hanxiao <chenhanxiao at gmail.com>
>>
>>If we insert or eject a CD-ROM/floppy device by:
>> 'virsh change-media VM --eject/--insert some.iso --live',
>>and the original CD-ROM device was configed with a boot order,
>>we may get:
>>  unsupported configuration: boot order 2 is already used by another device
>>
>>We just updated 'source file' section rather than hotplug a new device.
>>This check should be skipped in this case.
>>
>
>Attempting to change the boot index on update won't work and should be
>forbidden, as stated in the review for v1:
>https://www.redhat.com/archives/libvir-list/2018-January/msg00178.html
>

My case is not try to change boot index, but to change-media:

1) boot a VM with a CD-ROM, a centos7.1 ISO inside
2) change iso from centos7.3 to centos7.2 by:
#  change-media c72 hda   /media/b/ISO/CentOS-7-x86_64-DVD-1611.iso  --live
Successfully updated media.

This works and we can see cd-rom changed inside guest.

But if we had <boot order>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/media/b/IMG/c72.qcow2'/>
      <target dev='vda' bus='virtio'/>
 +    <boot order='1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/media/b/ISO/CentOS-7-x86_64-DVD-1511.iso'/>
      <target dev='hda' bus='ide'/>
      <readonly/>
 +    <boot order='2'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

Then change media will fail:
 #  change-media c72 hda   /media/b/ISO/CentOS-7-x86_64-DVD-1511.iso  --live
error: Failed to complete action update on media
error: unsupported configuration: boot order 2 is already used by another device

This is a common case when install OS with multiple DVDs,
or change DVD media when guest is active.

>>Signed-off-by: Chen Hanxiao <chenhanxiao at gmail.com>
>>---
>>v2:
[...]
>>+        /* Skip check for insert or eject CD-ROM device */
>>+        if (disk_device == VIR_DOMAIN_DISK_DEVICE_FLOPPY ||
>>+            disk_device == VIR_DOMAIN_DISK_DEVICE_CDROM) {
>
>Even though cdrom hotplug is not supported by libvirt, assuming that
>we're dealing with an update just because of the device type is wrong:
>https://www.redhat.com/archives/libvir-list/2018-January/msg00180.html
>
>virDomainDefCompatibleDevice should be aware of the operation (attach
>vs. update) and behave accordingly (forbid duplicit bootindexes for
>attach and a bootindex change for update)
>

As we can successfully 'virsh change-media' without <boot order> of CD-ROM device,
should we forbid this case for a live domain?

Regards,
- Chen