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Date: Mon, 16 Sep 2013 18:14:01 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qdev-monitor: Avoid exiting when
 hot-plugging two devices with the same bootindex value
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: aliguori@us.ibm.com, gleb@redhat.com, Marcel Apfelbaum <marcel.a@redhat.com>, sw@weilnetz.de, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, afaerber@suse.de

On Mon, Sep 16, 2013 at 12:11:35PM +0200, Paolo Bonzini wrote:
> 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).

This refers to 1) here? That's nice but it's not really all that helpful.

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