On Oct 16 09:21, Dr. David Alan Gilbert wrote: > * 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.
This patch calls post_save *even if the save operation fails*. My reasoning was that I didn't want a failed migration to leave a still-running original QEMU instance in an invalid state. Was this misguided? If it was not, which error do you prefer to be returned from vmstate_save_state_v() in the case that both the save operation itself and the post_save call returned errors? -Aaron
