This is based on top of the recent capabilities update:

https://www.redhat.com/archives/libvir-list/2020-April/msg01490.html

Whole series can be fetched by:

git fetch https://gitlab.com/pipo.sk/libvirt.git deprecated-crash

and requires a qemu which includes Markus' patches adding the -compat
feature:

https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg05380.html

Note that it was pushed partially, for convenience I'm providing a
branch with the patches applied and rebased:

git fetch https://gitlab.com/pipo.sk/qemu.git compat-deprecated

The main idea is to add developers and other interested parties the
ability to enable the -compat options to crash qemu in cases when
deprecated QMP command is used and stop formating any deprecated
response.

The qemu code is not pushed yet and doesn't have any way to be detected
but I want to query whether such feature makes sense for developers.

Peter Krempa (3):
  qemu: capabilities: Introduce QEMU_CAPS_COMPAT_DEPRECATED
  qemu: conf: Add 'deprecated_debug' setting to qemu.conf
  qemu: command: Handle formatting of '-compat' options

 src/qemu/libvirtd_qemu.aug                       |  1 +
 src/qemu/qemu.conf                               | 11 +++++++++++
 src/qemu/qemu_capabilities.c                     |  4 ++++
 src/qemu/qemu_capabilities.h                     |  1 +
 src/qemu/qemu_command.c                          | 16 ++++++++++++++++
 src/qemu/qemu_conf.c                             |  2 ++
 src/qemu/qemu_conf.h                             |  2 ++
 src/qemu/test_libvirtd_qemu.aug.in               |  1 +
 tests/qemucapabilitiesdata/caps_5.1.0.x86_64.xml |  1 +
 9 files changed, 39 insertions(+)

-- 
2.26.2