Re: [Qemu-devel] [PATCH] migration: improve documentation of postcopy-ram

[Greg Kurz <groug@kaod.org>]

On Wed, 7 Feb 2018 15:55:01 +0000
"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:

> * Greg Kurz (groug@kaod.org) wrote:
> > This capability must have the same value on both source and destination,
> > otherwise migration fails (commit 875fcd013ab6 "migration: incoming
> > postcopy advise sanity checks").
> > 
> > Let's write it down in various places where postcopy-ram is documented.
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>  
> 
> Thanks,
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 

Who should pick this up ?

> > ---
> >  docs/devel/migration.rst |    4 ++--
> >  hmp-commands.hx          |    3 ++-
> >  qapi/migration.json      |   10 ++++++----
> >  3 files changed, 10 insertions(+), 7 deletions(-)
> > 
> > diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
> > index bf97080dac2f..9d1b7657f0cf 100644
> > --- a/docs/devel/migration.rst
> > +++ b/docs/devel/migration.rst
> > @@ -387,8 +387,8 @@ doesn't finish in a given time the switch is made to postcopy.
> >  Enabling postcopy
> >  -----------------
> >  
> > -To enable postcopy, issue this command on the monitor prior to the
> > -start of migration:
> > +To enable postcopy, issue this command on the monitor (both source and
> > +destination) prior to the start of migration:
> >  
> >  ``migrate_set_capability postcopy-ram on``
> >  
> > diff --git a/hmp-commands.hx b/hmp-commands.hx
> > index 15620c94d3fc..d26eb4119b9d 100644
> > --- a/hmp-commands.hx
> > +++ b/hmp-commands.hx
> > @@ -1041,7 +1041,8 @@ ETEXI
> >          .params     = "",
> >          .help       = "Followup to a migration command to switch the migration"
> >                        " to postcopy mode. The postcopy-ram capability must "
> > -                      "be set before the original migration command.",
> > +                      "be set on both source and destination before the "
> > +                      "original migration command .",
> >          .cmd        = hmp_migrate_start_postcopy,
> >      },
> >  
> > diff --git a/qapi/migration.json b/qapi/migration.json
> > index 4cd3d1315884..7f465a1902ce 100644
> > --- a/qapi/migration.json
> > +++ b/qapi/migration.json
> > @@ -327,8 +327,10 @@
> >  #          to speed up convergence of RAM migration. (since 1.6)
> >  #
> >  # @postcopy-ram: Start executing on the migration target before all of RAM has
> > -#          been migrated, pulling the remaining pages along as needed. NOTE: If
> > -#          the migration fails during postcopy the VM will fail.  (since 2.6)
> > +#          been migrated, pulling the remaining pages along as needed. The
> > +#          capacity must have the same setting on both source and target
> > +#          or migration will not even start. NOTE: If the migration fails during
> > +#          postcopy the VM will fail.  (since 2.6)
> >  #
> >  # @x-colo: If enabled, migration will never end, and the state of the VM on the
> >  #        primary side will be migrated continuously to the VM on secondary
> > @@ -742,8 +744,8 @@
> >  # @migrate-start-postcopy:
> >  #
> >  # Followup to a migration command to switch the migration to postcopy mode.
> > -# The postcopy-ram capability must be set before the original migration
> > -# command.
> > +# The postcopy-ram capability must be set on both source and destination
> > +# before the original migration command.
> >  #
> >  # Since: 2.5
> >  #
> >   
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>