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[libvirt] [RFC PATCH v2 0/3] Start fixing the pvpanic mess

The pvpanic mess is even bigger than anticipated.  Let's fix the monitor's
behavior (patch 1), get rid of all traces that the broken pvpanic existed
(patch 2), and give it a new name so that libvirt can detect a design
that works (patch 3).

All downstreams are urged to apply patches 1+2 as soon as they are
merged in QEMU.

Still, there are still other problems to solve.

In QEMU, exposing "-device isa-pvpanic" in the ACPI tables.  Quite frankly
I don't have the time to fix this.  We have ~3 months though.  Patch 3
should not be applied until it is fixed.

Also, libvirt needs to know under which circumstances to add "-device
isa-pvpanic", besides obviously the availability of the device.

IMHO it is just too complicated to retrofit all complications in
<on_crash>.  In fact, I suspect <on_crash> would match more closely QEMU's
"internal error" state, and it would be quite useful to add that to the
QEMU driver.

Thus, libvirt could add support for an <on_panic> element with the
following values:

- default, which depends on the hypervisor and is "crash" for Xen,
  "ignore" for everything else

- "crash", which is the only supported value on Xen and means "use
  the value of <on_crash>"

- ignore, which is the behavior of old libvirt that don't know pvpanic

- restart, destroy, preserve, rename-restart as for <on_crash>.  In
  particular, preserve can still use the crashed_guest_panicked status,
  thus keeping the API compatible.

- pause, to pause the VM (with a new substatus)

<on_panic> would also have a coredump='yes/no' attribute, where yes
is only valid if the element is *not* one of default/crash/ignore.
Only "default" and "ignore" would be accepted for QEMU that does not
support the isa-pvpanic device.

Ideally, the coredump attribute would be added to <on_crash> too
for simplicity (Xen would refuse coredump + rename-restart and
coredump + preserve).


Paolo Bonzini (3):
  vl: allow "cont" from panicked state
  pc: get rid of builtin pvpanic
  pvpanic: rename to isa-pvpanic

 gdbstub.c            |  3 ---
 hw/i386/pc_piix.c    |  8 --------
 hw/i386/pc_q35.c     |  6 ------
 hw/misc/pvpanic.c    | 16 +++-------------
 include/hw/i386/pc.h |  3 ---
 vl.c                 |  6 ++----
 6 files changed, 5 insertions(+), 37 deletions(-)


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