Re: [Qemu-devel] [PATCH v4 17/47] ivshmem: improve debug messages

["Marc-André Lureau" <mlureau@redhat.com>]

----- Original Message -----
> On 24.09.2015 13:37, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > 
> > Some misc improvements to ivshmem debug.
> > 
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  hw/misc/ivshmem.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> > index c4c130d..71a71fc 100644
> > --- a/hw/misc/ivshmem.c
> > +++ b/hw/misc/ivshmem.c
> > @@ -208,10 +208,13 @@ static void ivshmem_io_write(void *opaque, hwaddr
> > addr,
> >              if (vector < s->peers[dest].nb_eventfds) {
> >                  IVSHMEM_DPRINTF("Notifying VM %d on vector %d\n", dest,
> >                  vector);
> >                  event_notifier_set(&s->peers[dest].eventfds[vector]);
> > +            } else {
> > +                IVSHMEM_DPRINTF("Invalid destination vector %d on VM
> > %d\n",
> > +                                vector, dest);
> >              }
> >              break;
> >          default:
> > -            IVSHMEM_DPRINTF("Invalid VM Doorbell VM %d\n", dest);
> > +            IVSHMEM_DPRINTF("Unhandled write " TARGET_FMT_plx "\n", addr);
> >      }
> >  }
> >  
> > @@ -263,9 +266,9 @@ static void ivshmem_receive(void *opaque, const uint8_t
> > *buf, int size)
> >  {
> >      IVShmemState *s = opaque;
> >  
> > -    ivshmem_IntrStatus_write(s, *buf);
> > +    IVSHMEM_DPRINTF("ivshmem_receive 0x%02x size: %d\n", *buf, size);
> >  
> > -    IVSHMEM_DPRINTF("ivshmem_receive 0x%02x\n", *buf);
> > +    ivshmem_IntrStatus_write(s, *buf);
> >  }
> 
> I may understand how this went here, so these debug messages are clearly
> specific about this particular function.
> here you have "ivshmem_receive". Do you want to put () to help someone
> getting these messages after enabling debug to understand that he should
> look up this function?

sure, notice it was there before without ()

> In the other messages though you (and the previous code) have been less
> function-specific in the message.

imho this kind of debug messages should just give enough context to understand and locate them. It's not important whether or not they have the function name.


> >  
> >  static int ivshmem_can_receive(void * opaque)
> > @@ -592,6 +595,7 @@ static void ivshmem_use_msix(IVShmemState * s)
> >      PCIDevice *d = PCI_DEVICE(s);
> >      int i;
> >  
> > +    IVSHMEM_DPRINTF("use msix, present: %d\n", msix_present(d));
> >      if (!msix_present(d)) {
> >          return;
> >      }
> 
> hmm do you want to say "ivshmem_use_msix(): present: true/false?"
> Or do you want to say something more generic about MSI-X in this case?
> 
> As is the comment you have:
> 
> 1) if it is specific to this function behavior, it does not help to look up
> the correct function

It's actually easy to locate with a grep "use msix" in ivshmem code (the macro prepend IVHSMEM:)

> 2) if it is a more generic comment, it does not help to understand what is
> going on
> 
> Can you explain more what the purpose of that debug statement is?

It helps to trace what's going on, at least it helped me. But if it's superflous, we can remove it (though it's really only there to help developers)

> 
> Ciao
> 
> Claudio
>