[Qemu-devel] Re: [PATCH] savevm: print migration failure to stderr rather than monitor

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2011-01-07 at 09:51 +0100, Jan Kiszka wrote:
> Am 07.01.2011 08:18, Alex Williamson wrote:
> > monitor_print only does anything for foreground commands, so we
> > don't ever see this error message in the case of a 'migrate -d'.
> 
> Your change needlessly steals the error from the monitor console where
> it belongs if migrate is used without -d. IIRC, mon is NULL in detached
> mode, so only print to stderr if there is no alternative. Otherwise
> stick with the monitor for interactive use.

Indeed, mon is NULL.  That makes this an easy

if (mon) {
    monitor_printf()
} else {
    fprintf()
}

But I wonder if we should put the fprintf in the monitor_printf() path
so we're not just special casing this one user.  Should all
monitor_printfs go to stderr if there's no monitor?  Thanks,

Alex

> > It also doesn't do much good to print a monitor error message if
> > the migration is being driven by something like libvirt.  Both
> 
> There is not only libvirt. Please don't destroy HMP "experience".
> 
> Jan
> 
> > of these seem to be the typical usage scenarios, so we might as
> > well print this error to stderr so it can at least be found in
> > the log messages.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> > 
> >  savevm.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/savevm.c b/savevm.c
> > index 90aa237..c6b9b01 100644
> > --- a/savevm.c
> > +++ b/savevm.c
> > @@ -1543,7 +1543,7 @@ int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f)
> >  
> >          r = vmstate_save(f, se);
> >          if (r < 0) {
> > -            monitor_printf(mon, "cannot migrate with device '%s'\n", se->idstr);
> > +            fprintf(stderr, "cannot migrate with device '%s'\n", se->idstr);
> >              return r;
> >          }
> >      }
> > 
> > 
> > 
>