Re: [Qemu-devel] [Qemu-ppc] [QEMU PATCH v5 4/6] migration: migrate QTAILQ

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Jianjun Duan (duanj@linux.vnet.ibm.com) wrote:
> 
> 
> On 10/07/2016 09:32 AM, Paolo Bonzini wrote:
> > 
> > 
> > On 07/10/2016 18:31, Jianjun Duan wrote:
> >>
> >>
> >> On 10/07/2016 07:34 AM, Dr. David Alan Gilbert wrote:
> >>> * Paolo Bonzini (pbonzini@redhat.com) wrote:
> >>>>
> >>>>
> >>>> On 06/10/2016 21:01, Dr. David Alan Gilbert wrote:
> >>>>>>>> +                } else if (field->flags & VMS_LINKED) {
> >>>>>>>> +                    ret = field->info->get(f, addr, size, field);
> >>>>>>>>                  } else {
> >>>>>>>>                      ret = field->info->get(f, addr, size, NULL);
> >>>>>>>>  
> >>>>>>>> @@ -193,6 +197,8 @@ static const char *vmfield_get_type_name(VMStateField *field)
> >>>>>>>>  
> >>>>>>>>      if (field->flags & VMS_STRUCT) {
> >>>>>>>>          type = "struct";
> >>>>>>>> +    } else if (field->flags & VMS_LINKED) {
> >>>>>>>> +        type = "linked";
> >>>>>>>>      } else if (field->info->name) {
> >>>>>>>>          type = field->info->name;
> >>>>>>>>      }
> >>>>>>>> @@ -327,6 +333,8 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
> >>>>>>>>                  }
> >>>>>>>>                  if (field->flags & VMS_STRUCT) {
> >>>>>>>>                      vmstate_save_state(f, field->vmsd, addr, vmdesc_loop);
> >>>>>>>> +                } else if  (field->flags & VMS_LINKED) {
> >>>>>>>> +                    field->info->put(f, addr, size, field, vmdesc_loop);
> >>>>>>>>                  } else {
> >>>>>>>>                      field->info->put(f, addr, size, NULL, NULL);
> >>>>>>>>                  }
> >>>>
> >>>> Is VMS_LINKED needed at all, since the fields are unused for every
> >>>> VMStateInfo except qtailq?
> >>>
> >>> No, I think you could easily drop the VMS_LINKED and just always pass them in.
> >>
> >> It is needed if we want to use vmdesc_loop.
> > 
> > Just always pass it in, can't you?
> > 
> Could that lead to repetition of array elements? I know it depends on
> individual put details.

I don't think so; Paolo is just suggesting replacing:

 +                } else if  (field->flags & VMS_LINKED) {
 +                    field->info->put(f, addr, size, field, vmdesc_loop);
                  } else {
                      field->info->put(f, addr, size, NULL, NULL);
                  }

by:

                  } else {
 -                    field->info->put(f, addr, size, NULL, NULL);
 +                    field->info->put(f, addr, size, field, vmdesc_loop);
                  }

most get/put won't use the field/vmdesc_loop so it wont matter.

Dave

> 
> Thanks,
> Jianjun
> > Paolo
> > 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK