Bug 1543775

(In reply to jiyan from comment #0)
> This bug is trying to track some issues in BZ#1434451
> (https://bugzilla.redhat.com/show_bug.cgi?id=1434451#c34) that are not be
> fixed in RHEL7.5
> 
> Description of problem:
> 1. 'update-deive' with alias in disk did not work actually
> 2. 'cold-plug' device with alias to running VM will fail in dumpxml file
> while succeed in cmd
> 
> Version-Release number of selected component (if applicable):
> libvirt-3.9.0-12.virtcov.el7.x86_64
> qemu-kvm-rhev-2.10.0-20.el7.x86_64
> kernel-3.10.0-847.el7.x86_64
> 
> How reproducible:
> 100%
> 
> Steps to Reproduce:
> Issue1: Prepare a VM with virtual disk in it and xml file describing virtual
> disk with different alias from original disk in VM, then update device 
> # virsh domstate test
> shut off
> 
> # virsh start test
> Domain test started
> 
> # virsh dumpxml test |grep "<disk" -A8
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='qcow2'/>
>       <source file='/var/lib/libvirt/images/RHEL-7.5-x86_64-latest.qcow2'/>
>       <backingStore/>
>       <target dev='hda' bus='virtio'/>
>       <alias name='virtio-disk0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
> function='0x0'/>
>     </disk>
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='raw'/>
>       <source file='/var/lib/libvirt/images/one.raw'/>
>       <backingStore/>
>       <target dev='hdb' bus='virtio'/>
>       <alias name='virtio-disk1'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x09'
> function='0x0'/>
>     </disk>
> 
> # cat hdb.xml 
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='raw'/>
>       <source file='/var/lib/libvirt/images/one.raw'/>
>       <target dev='hdb' bus='virtio'/>
>       <alias name='ua-disk-update1'/>
>     </disk>
> 
> # virsh update-device test hdb.xml 
> Device updated successfully

This should be fixed upstream by:

commit d0204e373d8aec51b1fd63783eeaa9a2015832ac
Author:     Michal Privoznik <mprivozn>
AuthorDate: Wed Dec 13 15:12:01 2017 +0100
Commit:     Michal Privoznik <mprivozn>
CommitDate: Fri Jan 5 14:22:45 2018 +0100

    qemuDomainDiskChangeSupported: Forbid alias change
    
    Since we have user aliases it may happen that users want to
    change it using 'update-device'. Instead of ignoring it silently,
    error out loudly. Note that we don't limit the check just for
    "ua-" prefixes because users might try to change libvirt
    generated aliases too.
    
    Signed-off-by: Michal Privoznik <mprivozn>
    Reviewed-by: John Ferlan <jferlan>

> 
> Issue2: Prepare a running VM with the following alias configuration, and xml
> file describing interface device, cold-plug interface device to running VM
> # virsh domstate test
> running
> 
> # virsh dumpxml test |grep alias
>       <alias name='virtio-disk0'/>
>       <alias name='virtio-disk1'/>
>       <alias name='usb'/>
>       <alias name='usb'/>
>       <alias name='usb'/>
>       <alias name='usb'/>
>       <alias name='pci.0'/>
>       <alias name='ua-IDE1'/>
>       <alias name='virtio-serial0'/>
>       <alias name='fdc0'/>
>       <alias name='net0'/>
>       <alias name='ua-myinterface'/>
>       <alias name='serial0'/>
>       <alias name='serial0'/>
>       <alias name='channel0'/>
>       <alias name='input0'/>
>       <alias name='input1'/>
>       <alias name='input2'/>
>       <alias name='sound0'/>
>       <alias name='video0'/>
>       <alias name='redir0'/>
>       <alias name='redir1'/>
>       <alias name='balloon0'/>
> 
> # cat interface.xml 
>  <interface type='network'>
>   <source network='default' bridge='virbr0'/>
>  <alias name='ua-myinterface'/>
>  </interface>
> 
> # virsh attach-device test interface.xml --config
> error: Failed to attach device from interface.xml
> error: XML error: non unique alias detected: usb

I think this is fixed by the following proposed patch:

https://www.redhat.com/archives/libvir-list/2018-February/msg00282.html

I've created a scratch build with those patches applied if you want to give it a try:

https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=15264067

*** Bug 1553162 has been marked as a duplicate of this bug. ***

I've merged the fix upstream:

commit e5673ed44465edcfccdd906158136ad8dcb94b9b
Author:     Michal Privoznik <mprivozn>
AuthorDate: Fri Mar 9 08:31:44 2018 +0100
Commit:     Michal Privoznik <mprivozn>
CommitDate: Mon Mar 12 13:27:24 2018 +0100

    virDomainDeviceValidateAliasForHotplug: Use correct domain defintion
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1553075
    
    For some weird reason this function is getting live and
    persistent def for domain but then accesses vm->def and
    vm->newDef directly. This is rather unsafe as we can be
    accessing NULL pointer.
    
    Signed-off-by: Michal Privoznik <mprivozn>

v4.1.0-91-ge5673ed44

Verified on: libvirt-4.5.0-2.virtcov.el7.x86_64 qemu-kvm-rhev-2.12.0-7.el7.x86_64:
I. Try to update device alias lively:
1. Prepare a running VM, two device XMLs only their aliases differ
# virsh list
 Id    Name                           State
----------------------------------------------------
 74    usb                            running

# cat /tmp/nic.xml 
    <interface type='network'>
      <mac address='52:54:00:72:7a:34'/>
      <source network='default'/>
      <model type='virtio'/>
      <alias name='ua-09f558d3-1223-4e82-9334-87b1eeb26925'/>
    </interface>

# cat /tmp/nic-alias1.xml 
    <interface type='network'>
      <mac address='52:54:00:72:7a:34'/>
      <source network='default'/>
      <model type='virtio'/>
      <alias name='ua-Alias'/>
    </interface>

2.Attach device, then try to change alias via update-device
# virsh attach-device usb /tmp/nic.xml       
Device attached successfully

# virsh update-device usb /tmp/nic-alias1.xml
error: Failed to update device from /tmp/nic-alias1.xml
error: operation forbidden: changing device alias is not allowed


II. Try to update device alias inactively:
# virsh attach-device usb /tmp/nic.xml  --config                                
Device attached successfully

# virsh update-device usb /tmp/nic-alias1.xml --config
Device updated successfully

# virsh dumpxml usb --inactive|awk '/<inter/,/<\/inter/'|grep ua
      <alias name='ua-Alias'/>

Alias changed.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2018:3113