Re: [Qemu-devel] [RFC PATCH v2 0/3] Start fixing the pvpanic mess

[Paolo Bonzini]

Il 21/08/2013 18:55, Daniel P. Berrange ha scritto:
> On Wed, Aug 21, 2013 at 06:51:11PM +0200, Paolo Bonzini wrote:
>> Il 21/08/2013 18:48, Daniel P. Berrange ha scritto:
>>> No, <on_crash> is the right thing to be using for this from
>>> libvirt's pov & I don't think we should invent something new.
>>> The <on_crash> element has always been intended to represent
>>> handling of guest panics, not qemu internal errors.
>>
>> Actually for Xen HVM guests, it mostly traps things such as failed
>> vmentries.  The Xen PV-on-HVM drivers do not register a panic notifier
>> that moves the guest to the "crashed" state.
>>
>> <on_crash> cannot be salvaged, in my opinion, because all domain XMLs in
>> the wild will have a setting that causes libvirt to add "-device
>> isa-pvpanic".  Thus changing libvirt versions will change guest
>> hardware, which is _very_ bad.
>>
>> In addition, Windows XP and 2003 will show the annoying device wizard
>> upon a libvirt upgrade, and fixing this is what surfaced all the mess.
> 
> The existance of a <on_crash> element should not be having any
> effect on what hardware we create. That is merely a lifecycle
> policy setting that should be completely independant of the
> guest device model.
> 
> eg it is valid to have <on_crash> present in the XML at all
> times, even if there's no pvpanic device present. That simply
> means the actions will never be triggered.

So are you suggesting to add a <pvpanic/> element to <devices>?  That
may be fine, but it doesn't seem very user-friendly.

Paolo