On 04/27/2018 12:34 PM, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > Update the migration docs: > > Among other changes: > * Added a general list of advice for device authors > * Reordered the section on conditional state (subsections etc) > into the order we prefer. > * Add a note about firmware > > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > --- > docs/devel/migration.rst | 531 +++++++++++++++++++++++++++------------ > 1 file changed, 375 insertions(+), 156 deletions(-)
> + > +General advice for device developers > +------------------------------------ > + > +- The migration state saved should reflect the device being modelled rather > + than the way your implementation works. That way if you change the > implementation Three spaces between sentences is unusual. > + > +- The migration might happen at an inconvenient point, > + e.g. right in the middle of the guest reprogramming the device, during > + guest reboot or shutdown or while the device is waiting for external IO. > + It's strongly preferred that migrations do not fail in this situation, > + since in the cloud environment migrations might happen automatically to > + VMs that the administrator doesn't directly control. Not for this patch, but is there any mechanism for a device to request that migration be delayed just long enough for the device to have a chance to get out of that inconsistent state, rather than having to migrate the inconvenient state? > +When we migrate a device, we save/load the state as a series > +of fields. Some times, due to bugs or new functionality, we need to Sometimes > @@ -328,9 +329,12 @@ Sometimes members of the VMState are no longer needed: > > - removing them will break migration compatibility > > - - making them version dependent and bumping the version will break > backwards migration compatibility. > + - making them version dependent and bumping the version will break > backward migration compatibility. Is it worth worrying about long lines? -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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