[Pkg-libvirt-maintainers] Bug#1107536: Bug#1107536: PPC64LE: Device hotplug/unplug requires guest reboot

[Trupti]

On 2025-06-10 12:29, Trupti wrote:
> On 2025-06-09 23:38, Andrea Bolognani wrote:
>> On Mon, Jun 09, 2025 at 09:50:24AM +0530, Trupti wrote:
>>> Package: libvirt-daemon
>>> Severity: important
>>> Tags: trixie ppc64el
>>> 
>>> Version Info:
>>> 
>>> Host/Guest OS: Debian Trixie/sid (powerpc64le)
>>> Kernel: 6.12.27-powerpc64le-64k
>>> QEMU: 10.0.0
>>> Libvirt: 11.3.0
>>> 
>>> Issue:
>>> 
>>> Live-attaching or detaching a device with virsh on a Debian Trixie 
>>> (ppc64le)
>>> guest does not take effect immediately. While the host command 
>>> succeeds, the
>>> guest OS only recognizes the change after a full reboot. This defeats 
>>> the
>>> purpose of the hotplug feature.
>>> 
>>> Steps to reproduce:
>>> 1) Start a guest with Debian-Trixie OS same as Host
>>> 2) Attach an interface to guest using below virsh attach-device 
>>> command
>>>    'virsh attach-interface --live vm bridge --source virbr0'
>>> 3) The command executes successfully and give output as "Interface 
>>> attached
>>> successfully"
>>> 4) But the interface is not immediately attached to guest. When the 
>>> guest is
>>> rebooted , then the
>>>    interface is seen on the guest.
>>> 5) Same is happening with virsh detach-interface command. A guest 
>>> reboot is
>>> required to remove
>>>    the interface from guest
>> 
>> What's the output of attach-interface if you pass the --print-xml
>> flag to it? What does the full live XML look like before and after
>> the operation?
>> 
>    I have gathered the diagnostic information you requested.
> 
>    virsh attach-interface --live vm bridge --source virbr0 --print-xml
> 
>    The command produced the following output:
>    <interface type='bridge'>
>       <source bridge='virbr0'/>
>    </interface>
> 
>     I have attached the two files, before.xml and after.xml.
> 
> 
>> Honestly this sounds like a guest OS issue rather than a bug in
>> libvirt. Is any message produced in dmesg/journal as a consequence of
>> the hotplug operation?
> 
> 
> The guest dmesg shows the RTAS hot-plug signal, but no further messages 
> appear.
> 
> 
> Thanks Trupti


Hello,

I have a key update from further testing.

Libvirt appears to be working correctly, as the VM's live XML is updated 
immediately after an attach-interface command.

The main finding comes from the guest kernel log. It reveals that both 
attach-interface and detach-interface cause the guest to receive the 
exact same signal: RTAS Hotplug Event (229).

Receiving the same signal for both adding and removing a device is the 
probable cause of the hotplug failure.

Thanks Trupti.