[libvirt] pvpanic plans?

[Eric Blake]

On 10/31/2013 08:47 AM, Michael S. Tsirkin wrote:

>>>      if (event & PVPANIC_PANICKED) {
>>>          panicked_mon_event("pause");
>>> -        vm_stop(RUN_STATE_GUEST_PANICKED);
>>
>> Don't you still need to halt the guest on a panic event, for management
>> to have a chance to choose what to do about the panic?
> 
> Guest can just call hlt to do this. Most guests do this on a panic
> already.

On the one hand, the fact that the guest already has to inform the host
means we are already trusting the guest behavior on a panic.  On the
other hand, assuming that the guest will ALWAYS halt after triggering a
panic is putting a lot more trust in the guest, compared to qemu
explicitly halting the guest so that management has a chance to choose
to dump the guest's state at the moment the panic was flagged.

The biggest argument for either removing all auto-pvpanic, or reverting
pvpanic altogether, is that no one seems to be actively using pvpanic in
the field yet.  I wish we could get more feedback from Fujitsu as the
original patch authors on what they are looking for in a working
solution, rather than repeatedly second-guessing everything downstream
and delaying the eradication of the buggy behavior even longer.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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