> From: Paolo Bonzini [mailto:pbonz...@redhat.com]
> On 20/09/2016 14:39, Pavel Dovgalyuk wrote:
> > > > + replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));
> > > > +
> > > > replay_enable(fname, mode);
> > > >
> > >
> > > Should you set snapshot = 1 here if there is no rrsnapshot option?
> >
> > No, because there is default snapshot name for the case when user
> > specifies overlay for the drives.
>
> There are three possibilities:
>
> a) these patches:
> with implicit overlay:
> -drive file=disk.raw,if=none,id=img-direct
> -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
>
> with explicit overlay:
> -drive file=disk.raw,if=none,id=img-direct
> -drive
> driver=blkreplay,if=none,image=img-direct,id=img-blkreplay,overlay=foo.qcow2
>
> Advantages:
> - does the right thing in the "implicit overlay" case.
- automatically creates overlay
>
> Disadvantages:
> - no need really to specify disk.raw in the "explicit overlay" case, since
> it's already specified when you create the overlay with qemu-img.
>
> Vote for implicit overlay: excellent
> Vote for explicit overlay: bad (need to track two file names)
Disadvantage is for replay only. Running QEMU in record mode automatically
creates overlay. Therefore two filenames are required.
> c) no rrsnapshot implies -snapshot:
> without overlay:
> -drive file=disk.raw,if=none,id=img-direct
> -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
>
> with overlay:
> -drive file=foo.qcow2,if=none,id=img-direct
> -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
> -icount ...,rrsnapshot=snapname
But how record will create this overlay?
This method requires creating overlay manually, because backing file is
not specified at all.
Pavel Dovgalyuk
