* Richard Henderson (richard.hender...@linaro.org) wrote:
> On 10/10/18 1:37 PM, Aaron Lindsay wrote:
> > In some cases it may be helpful to modify state before saving it for
> > migration, and then modify the state back after it has been saved. The
> > existing pre_save function provides half of this functionality. This
> > patch adds a post_save function to provide the second half.
> >
> > Signed-off-by: Aaron Lindsay <aclin...@gmail.com>
> > ---
> > docs/devel/migration.rst | 9 +++++++--
> > include/migration/vmstate.h | 1 +
> > migration/vmstate.c | 10 +++++++++-
> > 3 files changed, 17 insertions(+), 3 deletions(-)
>
> Hmm, maybe. I believe the common practice is for pre_save to copy state into
> a
> separate member on the side, so that conversion back isn't necessary.
>
> Ccing in the migration maintainers for a second opinion.
It is common to copy stuff into a separate member; however we do
occasionally think that post_save would be a useful addition; so I think
we should take it (if nothing else it actually makes stuff symmetric!).
Please make it return 'int' in the same way that pre_save/pre_load
does, so that it can fail and stop the migration.
Dave
>
>
> r~
>
> >
> > diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
> > index 687570754d..2a2533c9b3 100644
> > --- a/docs/devel/migration.rst
> > +++ b/docs/devel/migration.rst
> > @@ -419,8 +419,13 @@ The functions to do that are inside a vmstate
> > definition, and are called:
> >
> > This function is called before we save the state of one device.
> >
> > -Example: You can look at hpet.c, that uses the three function to
> > -massage the state that is transferred.
> > +- ``void (*post_save)(void *opaque);``
> > +
> > + This function is called after we save the state of one device
> > + (even upon failure, unless the call to pre_save returned and error).
> > +
> > +Example: You can look at hpet.c, that uses the first three functions
> > +to massage the state that is transferred.
> >
> > The ``VMSTATE_WITH_TMP`` macro may be useful when the migration
> > data doesn't match the stored device data well; it allows an
> > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> > index 2b501d0466..f6053b94e4 100644
> > --- a/include/migration/vmstate.h
> > +++ b/include/migration/vmstate.h
> > @@ -185,6 +185,7 @@ struct VMStateDescription {
> > int (*pre_load)(void *opaque);
> > int (*post_load)(void *opaque, int version_id);
> > int (*pre_save)(void *opaque);
> > + void (*post_save)(void *opaque);
> > bool (*needed)(void *opaque);
> > VMStateField *fields;
> > const VMStateDescription **subsections;
> > diff --git a/migration/vmstate.c b/migration/vmstate.c
> > index 0bc240a317..9afc9298f3 100644
> > --- a/migration/vmstate.c
> > +++ b/migration/vmstate.c
> > @@ -387,6 +387,9 @@ int vmstate_save_state_v(QEMUFile *f, const
> > VMStateDescription *vmsd,
> > if (ret) {
> > error_report("Save of field %s/%s failed",
> > vmsd->name, field->name);
> > + if (vmsd->post_save) {
> > + vmsd->post_save(opaque);
> > + }
> > return ret;
> > }
> >
> > @@ -412,7 +415,12 @@ int vmstate_save_state_v(QEMUFile *f, const
> > VMStateDescription *vmsd,
> > json_end_array(vmdesc);
> > }
> >
> > - return vmstate_subsection_save(f, vmsd, opaque, vmdesc);
> > + ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc);
> > +
> > + if (vmsd->post_save) {
> > + vmsd->post_save(opaque);
> > + }
> > + return ret;
> > }
> >
> > static const VMStateDescription *
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
