Re: [PATCH v2 3/5] qemu_passt: Make passt report errors to stderr whenever possible

[Laine Stump <laine@xxxxxxxxxx>]

On 2/16/23 11:27 AM, Michal Prívozník wrote:
> On 2/16/23 17:07, Stefano Brivio wrote:
> > On Thu, 16 Feb 2023 14:32:50 +0100
> > Michal Privoznik <mprivozn@xxxxxxxxxx> wrote:
> >
> > > Passt has '--stderr' argument which makes it report error onto
> > > stderr rather to system log. Unfortunately, it's currently
> > > impossible to use both '--log-file' and '--stderr', so pass the
> > > latter only if the former isn't passed. Then, use the stderr to
> > > produce more user friendly error message on failed start.
> > >
> > > Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
> > > ---
> > >   src/qemu/qemu_passt.c | 22 +++++++++++++++++++---
> > >   1 file changed, 19 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/src/qemu/qemu_passt.c b/src/qemu/qemu_passt.c
> > > index c082c149cd..881205449b 100644
> > > --- a/src/qemu/qemu_passt.c
> > > +++ b/src/qemu/qemu_passt.c
> > > @@ -171,8 +171,13 @@ qemuPasstStart(virDomainObj *vm,
> > >       if (net->sourceDev)
> > >           virCommandAddArgList(cmd, "--interface", net->sourceDev, NULL);
> > >   
> > > -    if (net->backend.logFile)
> > > +    if (net->backend.logFile) {
> > >           virCommandAddArgList(cmd, "--log-file", net->backend.logFile, NULL);
> > > +    } else {
> > > +        /* By default, passt logs into system logger. But we are interested
> > > +         * into errors too. Make it print errors onto stderr. */
> > > +        virCommandAddArg(cmd, "--stderr");
> > > +    }
> >
> > There's no need for this, see my previous email, archived at:
> >    https://listman.redhat.com/archives/libvir-list/2023-February/237880.html
> >
> > >   
> > >       /* Add IP address info */
> > >       for (i = 0; i < net->guestIP.nips; i++) {
> > > @@ -265,8 +270,19 @@ qemuPasstStart(virDomainObj *vm,
> > >           goto error;
> > >   
> > >       if (cmdret < 0 || exitstatus != 0) {
> > > -        virReportError(VIR_ERR_INTERNAL_ERROR,
> > > -                       _("Could not start 'passt': %s"), NULLSTR(errbuf));
> > > +        if (STRNEQ_NULLABLE(errbuf, "")) {
> > > +            virReportError(VIR_ERR_INTERNAL_ERROR,
> > > +                           _("Could not start 'passt': %s"), errbuf);
> > > +        } else if (net->backend.logFile) {
> > > +            virReportError(VIR_ERR_INTERNAL_ERROR,
> > > +                           _("Could not start 'passt': look into %s for error"),
> > > +                           net->backend.logFile);
> >
> > ...and this won't be needed either, with Laine's series for passt. It
> > might actually be a bit misleading.
> >
> > > +        } else {
> > > +            virReportError(VIR_ERR_INTERNAL_ERROR,
> > > +                           _("Could not start 'passt': exit status = '%d'"),
> > > +                           exitstatus);
> > > +        }
> > > +
> > >           goto error;
> > >       }
> > >   
> >
> > So all in all I think this is unnecessary, but also kind of harmless.
>
> Except those patches are not merged yet. And as we are getting close to
> the release I'd like to make this work with what we have now. We've been
> burned plenty of times with QEMU to learn our lesson. We've merged
> patches that were based not on QEMU's git, but some patches on top
> thinking - yeah, the API won't change. And then it did.

The patches are in passt, not QEMU, and Stefano will be cutting a new 
passt release "within a day or two".

> Now we don't require a release (which would be ideal), but at least for
> patches to be merged. When they get merged then yeah, this can be reworked.