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

[Paolo Bonzini <pbonzini@redhat.com>]

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


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(-)

-- 
1.8.3.1