Re: [PATCH v4 03/10] build: move COLO under CONFIG_REPLICATION

[Peter Xu]

On Fri, Apr 28, 2023 at 10:49:21PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> We don't allow to use x-colo capability when replication is not
> configured. So, no reason to build COLO when replication is disabled,
> it's unusable in this case.
> 
> Note also that the check in migrate_caps_check() is not the only
> restriction: some functions in migration/colo.c will just abort if
> called with not defined CONFIG_REPLICATION, for example:
> 
>     migration_iteration_finish()
>        case MIGRATION_STATUS_COLO:
>            migrate_start_colo_process()
>                colo_process_checkpoint()
>                    abort()
> 
> It could probably make sense to have possibility to enable COLO without
> REPLICATION, but this requires deeper audit of colo & replication code,
> which may be done later if needed.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Acked-by: Dr. David Alan Gilbert <dave@treblig.org>
> ---
>  hmp-commands.hx                |  2 ++
>  migration/colo.c               | 28 ------------------------
>  migration/meson.build          |  6 ++++--
>  migration/migration-hmp-cmds.c |  2 ++
>  migration/migration.c          |  6 ++++++
>  qapi/migration.json            |  9 +++++---
>  stubs/colo.c                   | 39 ++++++++++++++++++++++++++++++++++
>  stubs/meson.build              |  1 +
>  8 files changed, 60 insertions(+), 33 deletions(-)
>  create mode 100644 stubs/colo.c
> 
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index bb85ee1d26..fbd0932232 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1035,6 +1035,7 @@ SRST
>    migration (or once already in postcopy).
>  ERST
>  
> +#ifdef CONFIG_REPLICATION
>      {
>          .name       = "x_colo_lost_heartbeat",
>          .args_type  = "",
> @@ -1043,6 +1044,7 @@ ERST
>                        "a failover or takeover is needed.",
>          .cmd = hmp_x_colo_lost_heartbeat,
>      },
> +#endif
>  
>  SRST
>  ``x_colo_lost_heartbeat``
> diff --git a/migration/colo.c b/migration/colo.c
> index c9e0b909b9..6c7c313956 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -26,9 +26,7 @@
>  #include "qemu/rcu.h"
>  #include "migration/failover.h"
>  #include "migration/ram.h"
> -#ifdef CONFIG_REPLICATION
>  #include "block/replication.h"
> -#endif
>  #include "net/colo-compare.h"
>  #include "net/colo.h"
>  #include "block/block.h"
> @@ -86,7 +84,6 @@ void colo_checkpoint_delay_set(void)
>  static void secondary_vm_do_failover(void)
>  {
>  /* COLO needs enable block-replication */
> -#ifdef CONFIG_REPLICATION
>      int old_state;
>      MigrationIncomingState *mis = migration_incoming_get_current();
>      Error *local_err = NULL;
> @@ -151,14 +148,10 @@ static void secondary_vm_do_failover(void)
>      if (mis->migration_incoming_co) {
>          qemu_coroutine_enter(mis->migration_incoming_co);
>      }
> -#else
> -    abort();
> -#endif
>  }
>  
>  static void primary_vm_do_failover(void)
>  {
> -#ifdef CONFIG_REPLICATION
>      MigrationState *s = migrate_get_current();
>      int old_state;
>      Error *local_err = NULL;
> @@ -199,9 +192,6 @@ static void primary_vm_do_failover(void)
>  
>      /* Notify COLO thread that failover work is finished */
>      qemu_sem_post(&s->colo_exit_sem);
> -#else
> -    abort();
> -#endif
>  }
>  
>  COLOMode get_colo_mode(void)
> @@ -235,7 +225,6 @@ void colo_do_failover(void)
>      }
>  }
>  
> -#ifdef CONFIG_REPLICATION
>  void qmp_xen_set_replication(bool enable, bool primary,
>                               bool has_failover, bool failover,
>                               Error **errp)
> @@ -289,7 +278,6 @@ void qmp_xen_colo_do_checkpoint(Error **errp)
>      /* Notify all filters of all NIC to do checkpoint */
>      colo_notify_filters_event(COLO_EVENT_CHECKPOINT, errp);
>  }
> -#endif
>  
>  COLOStatus *qmp_query_colo_status(Error **errp)
>  {
> @@ -453,15 +441,11 @@ static int 
> colo_do_checkpoint_transaction(MigrationState *s,
>      }
>      qemu_mutex_lock_iothread();
>  
> -#ifdef CONFIG_REPLICATION
>      replication_do_checkpoint_all(&local_err);
>      if (local_err) {
>          qemu_mutex_unlock_iothread();
>          goto out;
>      }
> -#else
> -        abort();
> -#endif
>  
>      colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
>      if (local_err) {
> @@ -579,15 +563,11 @@ static void colo_process_checkpoint(MigrationState *s)
>      object_unref(OBJECT(bioc));
>  
>      qemu_mutex_lock_iothread();
> -#ifdef CONFIG_REPLICATION
>      replication_start_all(REPLICATION_MODE_PRIMARY, &local_err);
>      if (local_err) {
>          qemu_mutex_unlock_iothread();
>          goto out;
>      }
> -#else
> -        abort();
> -#endif
>  
>      vm_start();
>      qemu_mutex_unlock_iothread();
> @@ -755,7 +735,6 @@ static void 
> colo_incoming_process_checkpoint(MigrationIncomingState *mis,
>          return;
>      }
>  
> -#ifdef CONFIG_REPLICATION
>      replication_get_error_all(&local_err);
>      if (local_err) {
>          error_propagate(errp, local_err);
> @@ -772,9 +751,6 @@ static void 
> colo_incoming_process_checkpoint(MigrationIncomingState *mis,
>          qemu_mutex_unlock_iothread();
>          return;
>      }
> -#else
> -    abort();
> -#endif
>      /* Notify all filters of all NIC to do checkpoint */
>      colo_notify_filters_event(COLO_EVENT_CHECKPOINT, &local_err);
>  
> @@ -881,15 +857,11 @@ void *colo_process_incoming_thread(void *opaque)
>      object_unref(OBJECT(bioc));
>  
>      qemu_mutex_lock_iothread();
> -#ifdef CONFIG_REPLICATION
>      replication_start_all(REPLICATION_MODE_SECONDARY, &local_err);
>      if (local_err) {
>          qemu_mutex_unlock_iothread();
>          goto out;
>      }
> -#else
> -        abort();
> -#endif
>      vm_start();
>      qemu_mutex_unlock_iothread();
>      trace_colo_vm_state_change("stop", "run");
> diff --git a/migration/meson.build b/migration/meson.build
> index 480ff6854a..9c6a8e65d3 100644
> --- a/migration/meson.build
> +++ b/migration/meson.build
> @@ -13,8 +13,6 @@ softmmu_ss.add(files(
>    'block-dirty-bitmap.c',
>    'channel.c',
>    'channel-block.c',
> -  'colo-failover.c',
> -  'colo.c',
>    'exec.c',
>    'fd.c',
>    'global_state.c',
> @@ -30,6 +28,10 @@ softmmu_ss.add(files(
>    'threadinfo.c',
>  ), gnutls)
>  
> +if get_option('replication').allowed()
> +  softmmu_ss.add(files('colo-failover.c', 'colo.c'))
> +endif
> +
>  softmmu_ss.add(when: rdma, if_true: files('rdma.c'))
>  if get_option('live_block_migration').allowed()
>    softmmu_ss.add(files('block.c'))
> diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
> index 4e9f00e7dc..9885d7c9f7 100644
> --- a/migration/migration-hmp-cmds.c
> +++ b/migration/migration-hmp-cmds.c
> @@ -643,6 +643,7 @@ void hmp_migrate_start_postcopy(Monitor *mon, const QDict 
> *qdict)
>      hmp_handle_error(mon, err);
>  }
>  
> +#ifdef CONFIG_REPLICATION
>  void hmp_x_colo_lost_heartbeat(Monitor *mon, const QDict *qdict)
>  {
>      Error *err = NULL;
> @@ -650,6 +651,7 @@ void hmp_x_colo_lost_heartbeat(Monitor *mon, const QDict 
> *qdict)
>      qmp_x_colo_lost_heartbeat(&err);
>      hmp_handle_error(mon, err);
>  }
> +#endif
>  
>  typedef struct HMPMigrationStatus {
>      QEMUTimer *timer;
> diff --git a/migration/migration.c b/migration/migration.c
> index abcadbb619..0c14837cd3 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -389,6 +389,12 @@ void migration_incoming_disable_colo(void)
>  
>  int migration_incoming_enable_colo(void)
>  {
> +#ifndef CONFIG_REPLICATION
> +    error_report("ENABLE_COLO command come in migration stream, but COLO "
> +                 "module is not built in");
> +    return -ENOTSUP;
> +#endif
> +
>      if (ram_block_discard_disable(true)) {
>          error_report("COLO: cannot disable RAM discard");
>          return -EBUSY;
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 2c35b7b9cf..422a6b2613 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1381,7 +1381,8 @@
>  #
>  ##
>  { 'command': 'x-colo-lost-heartbeat',
> -  'features': [ 'unstable' ] }
> +  'features': [ 'unstable' ],
> +  'if': 'CONFIG_REPLICATION' }
>  
>  ##
>  # @migrate_cancel:
> @@ -1657,7 +1658,8 @@
>  ##
>  { 'struct': 'COLOStatus',
>    'data': { 'mode': 'COLOMode', 'last-mode': 'COLOMode',
> -            'reason': 'COLOExitReason' } }
> +            'reason': 'COLOExitReason' },
> +  'if': 'CONFIG_REPLICATION' }
>  
>  ##
>  # @query-colo-status:
> @@ -1674,7 +1676,8 @@
>  # Since: 3.1
>  ##
>  { 'command': 'query-colo-status',
> -  'returns': 'COLOStatus' }
> +  'returns': 'COLOStatus',
> +  'if': 'CONFIG_REPLICATION' }

I still see a bunch of other colo related definitions around in the qapi
schema, e.g. COLOExitReason.  Is it intended to leave them as is?

>  
>  ##
>  # @migrate-recover:
> diff --git a/stubs/colo.c b/stubs/colo.c
> new file mode 100644
> index 0000000000..cf9816d368
> --- /dev/null
> +++ b/stubs/colo.c
> @@ -0,0 +1,39 @@
> +#include "qemu/osdep.h"
> +#include "qemu/notify.h"
> +#include "net/colo-compare.h"
> +#include "migration/colo.h"
> +#include "migration/migration.h"
> +#include "qemu/error-report.h"
> +#include "qapi/qapi-commands-migration.h"
> +
> +void colo_shutdown(void)
> +{
> +}
> +
> +void *colo_process_incoming_thread(void *opaque)
> +{
> +    error_report("Impossible happend: trying to start COLO thread when COLO "
> +                 "module is not built in");
> +    abort();
> +}
> +
> +void colo_checkpoint_delay_set(void)
> +{
> +}
> +
> +void migrate_start_colo_process(MigrationState *s)
> +{
> +    error_report("Impossible happend: trying to start COLO when COLO "
> +                 "module is not built in");
> +    abort();
> +}
> +
> +bool migration_in_colo_state(void)
> +{
> +    return false;
> +}
> +
> +bool migration_incoming_in_colo_state(void)
> +{
> +    return false;
> +}
> diff --git a/stubs/meson.build b/stubs/meson.build
> index b2b5956d97..8412cad15f 100644
> --- a/stubs/meson.build
> +++ b/stubs/meson.build
> @@ -45,6 +45,7 @@ stub_ss.add(files('target-get-monitor-def.c'))
>  stub_ss.add(files('target-monitor-defs.c'))
>  stub_ss.add(files('trace-control.c'))
>  stub_ss.add(files('uuid.c'))
> +stub_ss.add(files('colo.c'))
>  stub_ss.add(files('vmstate.c'))
>  stub_ss.add(files('vm-stop.c'))
>  stub_ss.add(files('win32-kbd-hook.c'))
> -- 
> 2.34.1
> 

-- 
Peter Xu