[Qemu-devel] [PATCH for-1.6 V2 0/2] pvpanic: Separate pvpanic from machine type

[Marcel Apfelbaum <marcel.a@redhat.com>]

Creating the pvpanic device as part of the machine type has the
potential to trigger guest OS, guest firmware and driver bugs.
The potential of such was originally viewed as minimal.
However, since releasing 1.5 with pvpanic as part
of the builtin machine type, several issues were observed
in the field:
 - Some Windows versions triggered 'New Hardware Wizard' and
   an unidentified device appeared in Device Manager.
 - Issue reported off list: on Linux >= 3.10
   the pvpanic driver breaks the reset on crash option:
   VM stops instead of being reset.

pvpanic device also changes monitor command behaviour in some cases,
such silent incompatible changes aren't expected by management tools:
 - Monitor command requires 'cont' before 'system_reset'
   in order to restart the VM after kernel panic/BSOD 

Note that libvirt is the main user and libvirt people indicated their
preference to creating device with -device pvpanic rather than a
built-in one that can't be removed.

These issues were raised at last KVM call. The agreement reached
there was that we were a bit too rash to make the device
a builtin, and that for 1.6 we should drop the pvpanic device from the
default machine type, instead teach management tools to add it by
default using -device pvpanic.
It's not clear whether changing 1.5 behaviour at this point
is a sane thing, so this patchset doesn't touch 1.5 machine type.

This patch series reworks the patchset from Hu Tao
(don't create pvpanic device by default)
addressing comments and modifying behaviour according
to what was discussed on the call.
Please review and consider for 1.6.

A related discussion can be followed at 
http://lists.nongnu.org/archive/html/qemu-devel/2013-08/msg00036.html. 

This is a continuation of patches sent by Hu Tao:
http://lists.nongnu.org/archive/html/qemu-devel/2013-08/msg00124.html
http://lists.nongnu.org/archive/html/qemu-devel/2013-08/msg00125.html

Changes from v1 (by Hu Tao):
 - Keep pvpanic device enabled by default for 1.5
   for backport compatibility
 - Addressed Andreas Färber review (removed bus type)
 - Small changes to be posible to enable pvpanic
   both from command line and from machine_init
 - Added pvpanic to MISC category

Marcel Apfelbaum (2):
  hw/misc: don't create pvpanic device by default
  hw/misc: make pvpanic known to user

 hw/i386/pc_piix.c |  9 ++++-----
 hw/i386/pc_q35.c  |  7 ++++---
 hw/misc/pvpanic.c | 25 ++++++++++---------------
 3 files changed, 18 insertions(+), 23 deletions(-)

-- 
1.8.3.1