Re: [Qemu-devel] [PATCH] qdev-monitor: Avoid exiting when hot-plugging two devices with the same bootindex value

[Paolo Bonzini <pbonzini@redhat.com>]

Il 16/09/2013 11:54, Marcel Apfelbaum ha scritto:
> On Thu, 2013-09-12 at 13:04 +0200, Markus Armbruster wrote:
>> Marcel Apfelbaum <marcel.a@redhat.com> writes:
>>
>>> On Thu, 2013-09-12 at 11:43 +0200, Markus Armbruster wrote:
>>>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>>>
>>>>> Il 11/09/2013 20:26, Marcel Apfelbaum ha scritto:
>>>>>> Qemu is expected to quit if the same boot index value is used by
>>>>>> two devices.
>>>>>> However, hot-plugging a device with a bootindex value already used should
>>>>>> fail with a friendly message rather than quitting a running VM.
>>>>>
>>>>> I think the problem is right where QEMU exits, i.e. in
>>>>> add_boot_device_path.  This function should return an error instead, via
>>>>> an Error ** argument.
>>>>
>>>> Agree.
> 
> I understood that the boot order is passed in fw cfg and updated only once at
> "machine done". There is no update of this list after this point.
> Modifying the boot order from monitor does not work at all.
> 
> So in order to solve this issue we can:
> 1. Don't allow use of bootindex at hot-plug
> 2. Change the architecture so boot order changing during hot-plug will be possible.

This is done relatively easily in add_boot_device_path (check the
qdev_hotplug variable and return an error if it is 1).

You can do it on top of Markus's patch.

Paolo