[libvirt] discuss about pvpanic

[Michal Privoznik]

On 1/8/20 10:36 AM, Paolo Bonzini wrote:
> On 08/01/20 09:25, zhenwei pi wrote:
>> Hey, Paolo
>>
>> Currently, pvpapic only supports bit 0(PVPANIC_PANICKED).
>> We usually expect that guest writes ioport (typical 0x505) in panic_notifier_list callback
>> during handling panic, then we can handle pvpapic event PVPANIC_PANICKED in QEMU.
>>
>> On the other hand, guest wants to handle the crash by kdump-tools, and reboots without any
>> panic_notifier_list callback. So QEMU only knows that guest has rebooted (because guest
>> write 0xcf9 ioport for RCR request), but QEMU can't identify why guest resets.
>>
>> In production environment, we hit about 100+ guest reboot event everyday, sadly we
>> can't separate the abnormal reboot from normal operation.
>>
>> We want to add a new bit for pvpanic event(maybe PVPANIC_CRASHLOADED) to represent the guest has crashed,
>> and the panic is handled by the guest kernel. (here is the previous patch https://lkml.org/lkml/2019/12/14/265)
>>
>> What do you think about this solution? Or do you have any other suggestions?
> 
> Hi Zhenwei,
> 
> the kernel-side patch certainly makes sense.  I assume that you want the
> event to propagate up from QEMU to Libvirt and so on?  The QEMU patch
> would need to declare a new event (qapi/misc.json) and send it in
> handle_event (hw/misc/pvpanic.c).  For Libvirt I'm not familiar, so I'm
> adding the respective list.

Adding an event is fairly easy, if everything you want libvirt to do is 
report the event to upper layers. I volunteer to do it. Question is, how 
qemu is going to report this, whether some attributes to GUEST_PANICKED 
event or some new event. But more important is to merge the change into 
kernel.

Michal