[libvirt] [PATCH] qemu: add support for -device pvpanic

[Hu Tao]

On Wed, Nov 27, 2013 at 06:15:27AM -0700, Eric Blake wrote:
> On 11/27/2013 03:39 AM, Peter Krempa wrote:
> > On 11/27/13 09:41, Hu Tao wrote:
> >> qemu removes the builtin pvpanic device for all qemu versions since 1.7,
> >> in order to support <on_crash>, '-device pvpanic' has to be added to
> >> qemu command line.
> >>
> >> Signed-off-by: Hu Tao <hutao at cn.fujitsu.com>
> >> ---
> 
> > I remember discussions saying that it's NOT a good idea to enable this
> > stuff always. As a result, this device is not being added by qemu as you
> > described above. Shouldn't we only add this if the user enables
> > <on_crash> actions?
> 
> You are precisely right; we MUST add a new entry under <devices> in the
> <domain> XML before enabling this device.

Is a entry under <devices> for pvpanic still needed? What I thought is
that it is natural to enable pvpanic when user enables <on_crash>,
he/she even has no need to know about pvpanic.

> 
> See these threads for some ideas (although recall that qemu has been
> fixed in the meantime to state that any distro shipping a qemu with
> pvpanic enabled by default can be considered buggy, and that libvirt can
> now assume that pvpanic will not happen without an explicit '-device
> pvpanic'):
> https://www.redhat.com/archives/libvir-list/2013-August/msg01184.html
> https://www.redhat.com/archives/libvir-list/2013-August/msg01136.html

IIRC, at the time of the thread, the pvpanic entry under <devices> is
for addressing the compatibility of qemu 1.5(has builtin pvpanic) and
qemu 1.6 and after(has no builtin pvpanic). Since now qemu removes
builtin pvpanic for all versions, I think there is no need for pvpanic
entry in xml.


-- 
Regards,
Hu Tao