Re: [PATCH] fw_cfg: Allow reboot-timeout=-1 again

[Han Han]

However, another important question is: how can we avoid such undocumented incompatibility appears again?

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.

On Tue, Oct 29, 2019 at 1:59 PM Dr. David Alan Gilbert <address@hidden> wrote:

* Markus Armbruster (address@hidden) wrote:
> "Dr. David Alan Gilbert" <address@hidden> writes:
>
> > * Markus Armbruster (address@hidden) wrote:
> >> "Dr. David Alan Gilbert (git)" <address@hidden> writes:
> >>
> >> > From: "Dr. David Alan Gilbert" <address@hidden>
> >> >
> >> > 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 <address@hidden>
> >> > ---
> >> >  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:
> >> <address@hidden>.
> >
> > 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 / address@hidden / Manchester, UK

--

Best regards,

-----------------------------------

Han Han
Quality Engineer
Redhat.

Email: address@hidden
Phone: +861065339333