Re: 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