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

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* 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>

> ---
>  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