[Qemu-devel] Re: [PATCH V3] floppy: save and restore DIR register

[Jason Wang <jasowang@redhat.com>]

Paolo Bonzini writes:
 > On 04/01/2011 08:22 AM, Jason Wang wrote:
 > > +
 > > +    if (drive->bs == NULL) {
 > > +        return 1;
 > 
 > Is it okay to return 1 here?  Have you tested the case when both the 
 > source and the target drives have no floppy?
 > 

Thanks for the reminding, and it could be fixed by put all pre/post callbacks
into the subsections.

 > (The "media_changed == 2" in my sample code was basically a way to save 
 > the "media present" state of the drive on the source).
 > 

Right, but it would make subsection saving be the common case (consider most of
the vm may just have one floppy but we have two drives). A better solution maybe:

1 Set default_migration_media_changed be 0 for 0.15 and 1 for elder
2 Unconditiaonlly send subsection when it was 0, and do not send subsection when
it was 1
3 Set media_changed to default_migration_media_changed in pre_load()
4 Let all pre/post to be in subsection

After those, we can make sure the migration between 0.15 could get correct
media_changed, also make sure the seamless migration between 0.15 and older
machine types.

Any suggestions?

 > > +    } else {
 > > +        drive->bs->media_changed = drive->media_changed;
 > > +        return 0;
 > > +    }
 > 
 > The code is also missing the case of a pc-0.14 machine.  The problem 
 > here is that the pc-0.15 machine hasn't been created yet, you get the 
 > honor. :(
 > 

Would create such one :)

 > Paolo