Re: [PATCH V2 03/11] migration: save cpr mode

[Fabiano Rosas <farosas@suse.de>]

Steve Sistare <steven.sistare@oracle.com> writes:

> Save the mode in CPR state, so the user does not need to explicitly specify
> it for the target.  Modify migrate_mode() so it returns the incoming mode on
> the target.
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  include/migration/cpr.h |  7 +++++++
>  migration/cpr.c         | 23 ++++++++++++++++++++++-
>  migration/migration.c   |  1 +
>  migration/options.c     |  9 +++++++--
>  4 files changed, 37 insertions(+), 3 deletions(-)
>
> diff --git a/include/migration/cpr.h b/include/migration/cpr.h
> index 8e7e705..42b4019 100644
> --- a/include/migration/cpr.h
> +++ b/include/migration/cpr.h
> @@ -8,6 +8,13 @@
>  #ifndef MIGRATION_CPR_H
>  #define MIGRATION_CPR_H
>  
> +#include "qapi/qapi-types-migration.h"
> +
> +#define MIG_MODE_NONE MIG_MODE__MAX

What happens when a QEMU that knows about a new mode migrates into a
QEMU that doesn't know that mode, i.e. sees it as MIG_MODE__MAX?

I'd just use -1.

> +
> +MigMode cpr_get_incoming_mode(void);
> +void cpr_set_incoming_mode(MigMode mode);
> +
>  typedef int (*cpr_walk_fd_cb)(int fd);
>  void cpr_save_fd(const char *name, int id, int fd);
>  void cpr_delete_fd(const char *name, int id);
> diff --git a/migration/cpr.c b/migration/cpr.c
> index 313e74e..1c296c6 100644
> --- a/migration/cpr.c
> +++ b/migration/cpr.c
> @@ -21,10 +21,23 @@
>  typedef QLIST_HEAD(CprFdList, CprFd) CprFdList;
>  
>  typedef struct CprState {
> +    MigMode mode;
>      CprFdList fds;
>  } CprState;
>  
> -static CprState cpr_state;
> +static CprState cpr_state = {
> +    .mode = MIG_MODE_NONE,
> +};
> +
> +MigMode cpr_get_incoming_mode(void)
> +{
> +    return cpr_state.mode;
> +}
> +
> +void cpr_set_incoming_mode(MigMode mode)
> +{
> +    cpr_state.mode = mode;
> +}
>  
>  /****************************************************************************/
>  
> @@ -124,11 +137,19 @@ void cpr_resave_fd(const char *name, int id, int fd)
>  /*************************************************************************/
>  #define CPR_STATE "CprState"
>  
> +static int cpr_state_presave(void *opaque)
> +{
> +    cpr_state.mode = migrate_mode();
> +    return 0;
> +}
> +
>  static const VMStateDescription vmstate_cpr_state = {
>      .name = CPR_STATE,
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .pre_save = cpr_state_presave,
>      .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(mode, CprState),
>          VMSTATE_QLIST_V(fds, CprState, 1, vmstate_cpr_fd, CprFd, next),
>          VMSTATE_END_OF_LIST()
>      }
> diff --git a/migration/migration.c b/migration/migration.c
> index e394ad7..0f47765 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -411,6 +411,7 @@ void migration_incoming_state_destroy(void)
>          mis->postcopy_qemufile_dst = NULL;
>      }
>  
> +    cpr_set_incoming_mode(MIG_MODE_NONE);
>      yank_unregister_instance(MIGRATION_YANK_INSTANCE);
>  }
>  
> diff --git a/migration/options.c b/migration/options.c
> index 645f550..305397a 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -22,6 +22,7 @@
>  #include "qapi/qmp/qnull.h"
>  #include "sysemu/runstate.h"
>  #include "migration/colo.h"
> +#include "migration/cpr.h"
>  #include "migration/misc.h"
>  #include "migration.h"
>  #include "migration-stats.h"
> @@ -758,8 +759,12 @@ uint64_t migrate_max_postcopy_bandwidth(void)
>  
>  MigMode migrate_mode(void)
>  {
> -    MigrationState *s = migrate_get_current();
> -    MigMode mode = s->parameters.mode;
> +    MigMode mode = cpr_get_incoming_mode();
> +
> +    if (mode == MIG_MODE_NONE) {
> +        MigrationState *s = migrate_get_current();
> +        mode = s->parameters.mode;
> +    }
>  
>      assert(mode >= 0 && mode < MIG_MODE__MAX);
>      return mode;