Re: [Qemu-devel] [PATCH v3 2/5] migration: Introduce ignore-shared capability

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

* Yury Kotov (yury-kotov@yandex-team.ru) wrote:
> We want to use local migration to update QEMU for running guests.
> In this case we don't need to migrate shared (file backed) RAM.
> So, add a capability to ignore such blocks during live migration.
> 
> Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/migration.c | 14 ++++++++++++++
>  migration/migration.h |  1 +
>  qapi/migration.json   |  5 ++++-
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 37e06b76dc..0fadd97fb9 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -957,6 +957,11 @@ static bool migrate_caps_check(bool *cap_list,
>              error_setg(errp, "Postcopy is not supported");
>              return false;
>          }
> +
> +        if (cap_list[MIGRATION_CAPABILITY_X_IGNORE_SHARED]) {
> +            error_setg(errp, "Postcopy is not compatible with ignore-shared");
> +            return false;
> +        }
>      }
>  
>      return true;
> @@ -1983,6 +1988,15 @@ bool migrate_dirty_bitmaps(void)
>      return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_BITMAPS];
>  }
>  
> +bool migrate_ignore_shared(void)
> +{
> +    MigrationState *s;
> +
> +    s = migrate_get_current();
> +
> +    return s->enabled_capabilities[MIGRATION_CAPABILITY_X_IGNORE_SHARED];
> +}
> +
>  bool migrate_use_events(void)
>  {
>      MigrationState *s;
> diff --git a/migration/migration.h b/migration/migration.h
> index dcd05d9f87..4211995c53 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -261,6 +261,7 @@ bool migrate_release_ram(void);
>  bool migrate_postcopy_ram(void);
>  bool migrate_zero_blocks(void);
>  bool migrate_dirty_bitmaps(void);
> +bool migrate_ignore_shared(void);
>  
>  bool migrate_auto_converge(void);
>  bool migrate_use_multifd(void);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 7a795ecc16..7105570cd3 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -409,13 +409,16 @@
>  #           devices (and thus take locks) immediately at the end of migration.
>  #           (since 3.0)
>  #
> +# @x-ignore-shared: If enabled, QEMU will not migrate shared memory (since 4.0)
> +#
>  # Since: 1.2
>  ##
>  { 'enum': 'MigrationCapability',
>    'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
>             'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
>             'block', 'return-path', 'pause-before-switchover', 'x-multifd',
> -           'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate' ] }
> +           'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
> +           'x-ignore-shared' ] }
>  
>  ##
>  # @MigrationCapabilityStatus:
> -- 
> 2.20.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK