Re: [PATCH] tools: init-dom0less: Replace err() with more informative messages

[Jason Andryuk <jason.andryuk@xxxxxxx>]

On 2025-10-01 07:24, Orzel, Michal wrote:
> On 01/10/2025 12:09, Alejandro Vallejo wrote:
> > On Wed Oct 1, 2025 at 9:51 AM CEST, Michal Orzel wrote:
> > > Current use of err() has the following issues:
> > > - without setting errno, on error it results in printing e.g.:
> > >   "init-dom0less: writing to xenstore: Success"
> > >   This is very misleading and difficult to deduct that there was a
> > >   failure.
> > > - does not propagate error codes to the caller.
> > > - skips "init_domain failed" message by exiting early.
Maybe add another bullet:
 - The early exit prevents setting up any remaining domains.

That was my main motivation in my attempt at this change: 
https://lore.kernel.org/xen-devel/20250826210847.126015-7-jason.andryuk@xxxxxxx/.
Your re-written error messages are better though.

> > > Replace err() with more informative messages propagating rc when
> > > possible.
> > Sounds good to me. Only suggestion I'd make is to also print relevant arguments
> > where needed, like...
> >
> > > Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
> > > ---
> > >   tools/helpers/init-dom0less.c | 25 +++++++++++++++++--------
> > >   1 file changed, 17 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/tools/helpers/init-dom0less.c b/tools/helpers/init-dom0less.c
> > > index a182dce56353..3dd2d74886eb 100644
> > > --- a/tools/helpers/init-dom0less.c
> > > +++ b/tools/helpers/init-dom0less.c
> > > +    }
> > >   
> > >       rc = xs_introduce_domain(xsh, info->domid, xenstore_pfn, xenstore_evtchn);
> > > -    if (!rc)
> > > -        err(1, "xs_introduce_domain");
> > > +    if (!rc) {
> > > +        printf("Failed to introduce a domain\n");
> > > +        return 1;
> > nit: Maybe -EBUSY so it's -errno like the others?
> There are other places in this script where we return 1.
It's a mix of error as 1 or -errno, but at least success == 0 is consistent.

The xs_* functions set errno, so maybe here it would be good to return 
-errno.  I think moving toward -errno, which is more informative, would 
be an improvement.
Thanks,
Jason