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

[Greg Kurz]

On Wed, 14 Feb 2018 09:45:50 +0000
"Dr. David Alan Gilbert" <address@hidden> wrote:

> * Greg Kurz (address@hidden) wrote:
> > On Wed, 7 Feb 2018 15:55:01 +0000
> > "Dr. David Alan Gilbert" <address@hidden> wrote:
> >   
> > > * Greg Kurz (address@hidden) 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 <address@hidden>    
> > > 
> > > Thanks,
> > > 
> > > Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> > >   
> > 
> > Who should pick this up ?  
> 
> I was going to pick it up in a migration pull today.
> 

Cool, thanks !

> Dave
> 
> > > > ---
> > > >  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 / address@hidden / Manchester, UK
> > >   
> >   
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK