Re: [RFC PATCH 2/3] qemu: conf: Add 'deprecated_debug' setting to qemu.conf

On Thu, Apr 30, 2020 at 04:13:43PM +0200, Peter Krempa wrote: > New QEMU supports an harsh, but hard to ignore way to notify that the > QMP user used an deprecated command. This is useful e.g. for developers > to see that something needs to be fixed. > > This patch introduces a qemu.conf option to enable the setting in cases > when qemu supports it so that developers and continiuous integration > efforts are notified about use of deprecated fields while it's not late. > --- > src/qemu/libvirtd_qemu.aug | 1 + > src/qemu/qemu.conf | 11 +++++++++++ > src/qemu/qemu_conf.c | 2 ++ > src/qemu/qemu_conf.h | 2 ++ > src/qemu/test_libvirtd_qemu.aug.in | 1 + > 5 files changed, 17 insertions(+) > > diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug > index 404498b611..4cf700346f 100644 > --- a/src/qemu/libvirtd_qemu.aug > +++ b/src/qemu/libvirtd_qemu.aug > @@ -118,6 +118,7 @@ module Libvirtd_qemu = > > let debug_level_entry = int_entry "gluster_debug_level" > | bool_entry "virtiofsd_debug" > + | bool_entry "deprecated_debug" > > let memory_entry = str_entry "memory_backing_dir" > > diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf > index abdbf07fec..558731da0f 100644 > --- a/src/qemu/qemu.conf > +++ b/src/qemu/qemu.conf > @@ -852,3 +852,14 @@ > # may change across versions. > # > #capability_filters = [ "capname" ] > + > +# 'deprecated_debug' setting controls whether qemu should be instructed to crash > +# when libvirt uses deprecated commands or arguments and at the same time to > +# stop including deprecated fields in replies. This setting is meant for > +# developers and continious-integration efforts to make it obvious when > +# we rely on features which may go away. In cases when qemu doesn't support > +# dealing with deprecated fields the setting is ignored. > +# > +# DO NOT use in production. > +# > +#deprecated_debug = 1 Calling it "debug" when the result is to "crash" is a bit misleading ! I think this behaviour is a bit too harsh. As a developer I would be happy to enable an option in my qemu.conf to causes log messages to printed to stderr for all my dev servers & VMs, or gracefully rejects a QMP command with an error. I'm very unlikely to ever enable an option that is going to hard crash my VMs, because that risks data loss to me.