* Han Han (h...@redhat.com) wrote: > However, another important question is: how can we avoid such undocumented > incompatibility appears again?
The reboot-timeout one was accidental - it was a documented qemu feature; just no one noticed it when the input check was added. Officially if we actually want to deprecate a feature we should actually follow qemu's deprecation guidelines. > I can show another case caused by such incompatibile change: > https://bugzilla.redhat.com/show_bug.cgi?id=1745868#c0 > > For the qemu devices, attributes, values, qmp cmds, qmp cmds arguments used > by libvirt, could we get a way to inform libvirt > that an incompatibile qemu change is coming, please update libvirt code > ASAP to adjust to that change? > Or another way that is more gently: popping up the warning of depreciation > instead of dropping it, and then drop it in the version > after next version. Yes that should happen; with deprecated devices it's easier than more subtle features like command line things; I'm not sure how that gets introspected. I thought libvirt already asked qemu for a list of devices, so I'm confused why libvirt didn't spot it before starting the VM in 1745868. Dave > > On Tue, Oct 29, 2019 at 1:59 PM Dr. David Alan Gilbert <dgilb...@redhat.com> > wrote: > > > * Markus Armbruster (arm...@redhat.com) wrote: > > > "Dr. David Alan Gilbert" <dgilb...@redhat.com> writes: > > > > > > > * Markus Armbruster (arm...@redhat.com) wrote: > > > >> "Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> writes: > > > >> > > > >> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > > >> > > > > >> > Commit ee5d0f89de3e53cdb0dc added range checking on reboot-timeout > > > >> > to only allow the range 0..65535; however both qemu and libvirt > > document > > > >> > the special value -1 to mean don't reboot. > > > >> > Allow it again. > > > >> > > > > >> > Fixes: ee5d0f89de3e53cdb0dc ("fw_cfg: Fix -boot reboot-timeout > > error checking") > > > >> > RH bz: https://bugzilla.redhat.com/show_bug.cgi?id=1765443 > > > >> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > > > >> > --- > > > >> > hw/nvram/fw_cfg.c | 5 +++-- > > > >> > 1 file changed, 3 insertions(+), 2 deletions(-) > > > >> > > > > >> > diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c > > > >> > index 7dc3ac378e..1a9ec44232 100644 > > > >> > --- a/hw/nvram/fw_cfg.c > > > >> > +++ b/hw/nvram/fw_cfg.c > > > >> > @@ -247,10 +247,11 @@ static void fw_cfg_reboot(FWCfgState *s) > > > >> > > > > >> > if (reboot_timeout) { > > > >> > rt_val = qemu_opt_get_number(opts, "reboot-timeout", -1); > > > >> > + > > > >> > /* validate the input */ > > > >> > - if (rt_val < 0 || rt_val > 0xffff) { > > > >> > + if (rt_val < -1 || rt_val > 0xffff) { > > > >> > error_report("reboot timeout is invalid," > > > >> > - "it should be a value between 0 and > > 65535"); > > > >> > + "it should be a value between -1 and > > 65535"); > > > >> > exit(1); > > > >> > } > > > >> > } > > > >> > > > >> Semantic conflict with "PATCH] qemu-options.hx: Update for > > > >> reboot-timeout parameter", Message-Id: > > > >> <20191015151451.727323-1-h...@redhat.com>. > > > > > > > > Thanks for spotting that. > > > > I think Han and also submitted patches to review it from libvirt > > > > and it wasn't obvious what to do. (Cc'd Han in). > > > > > > > >> I'm too tired right now to risk an opinion on which one we want. > > > > > > > > As is everyone else ! The problem here is that its documented > > > > as a valid thing to do, and libvirt does it, and you might have > > > > a current XML file that did it. Now I think you could change libvirt > > > > to omit the reboot-timeout parameter if it was called with -1. > > > > > > > > So given its a documented thing in both qemu and libvirt xml > > > > if we want to remove it then it sohuld be deprecated properly - but > > it's > > > > already broken. > > > > > > Since commit ee5d0f89d, v4.0.0. > > > > > > If that commit had not made it into a release, we'd certainly treat the > > > loss of "-1 means don't reboot" as regression. > > > > > > But it has. We can treat it as a regression anyway. We can also > > > declare "ship has sailed". > > > > > > I'm leaning towads the former. > > > > > > If we restore "-1 means don't reboot", then I don't see a need to > > > deprecate it. Just keep it. > > > > > > What do you think? > > > > That's also my view; especially since the problem seems to be an easy > > fix. > > > > Dave > > > > -- > > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK > > > > > -- > Best regards, > ----------------------------------- > Han Han > Quality Engineer > Redhat. > > Email: h...@redhat.com > Phone: +861065339333 -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
