Re: [Qemu-devel] [PATCH 1/2] migration: Move check_migratable() into qdev.c

[Peter Xu <peterx@redhat.com>]

On Tue, Apr 25, 2017 at 12:17:57PM +0200, Juan Quintela wrote:
> The function is only used once, and nothing else in migration knows
> about objects.  Create the function vmstate_device_is_migratable() in
> savem.c that really do the bit that is related with migration.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  hw/core/qdev.c                | 15 ++++++++++++++-
>  include/migration/migration.h |  3 ---
>  include/migration/vmstate.h   |  2 ++
>  migration/migration.c         | 15 ---------------
>  migration/savevm.c            | 10 ++++++++++
>  stubs/vmstate.c               |  5 ++---
>  6 files changed, 28 insertions(+), 22 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 02b632f..17ff638 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -37,7 +37,7 @@
>  #include "hw/boards.h"
>  #include "hw/sysbus.h"
>  #include "qapi-event.h"
> -#include "migration/migration.h"
> +#include "migration/vmstate.h"
>  
>  bool qdev_hotplug = false;
>  static bool qdev_hot_added = false;
> @@ -861,6 +861,19 @@ static bool device_get_realized(Object *obj, Error **errp)
>      return dev->realized;
>  }
>  
> +static int check_migratable(Object *obj, Error **err)
> +{
> +    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> +    if (!vmstate_device_is_migratable(dc->vmsd)) {
> +        error_setg(err, "Device %s is not migratable, but "
> +                   "--only-migratable was specified",
> +                   object_get_typename(obj));
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
>  static void device_set_realized(Object *obj, bool value, Error **errp)
>  {
>      DeviceState *dev = DEVICE(obj);
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index ba1a16c..dfeca38 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -22,7 +22,6 @@
>  #include "qapi-types.h"
>  #include "exec/cpu-common.h"
>  #include "qemu/coroutine_int.h"
> -#include "qom/object.h"
>  
>  #define QEMU_VM_FILE_MAGIC           0x5145564d
>  #define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
> @@ -292,8 +291,6 @@ int migrate_add_blocker(Error *reason, Error **errp);
>   */
>  void migrate_del_blocker(Error *reason);
>  
> -int check_migratable(Object *obj, Error **err);
> -
>  bool migrate_release_ram(void);
>  bool migrate_postcopy_ram(void);
>  bool migrate_zero_blocks(void);
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index dad3984..9452dec 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -1049,4 +1049,6 @@ int64_t self_announce_delay(int round)
>  
>  void dump_vmstate_json_to_file(FILE *out_fp);
>  
> +bool vmstate_device_is_migratable(const VMStateDescription *vmsd);
> +
>  #endif
> diff --git a/migration/migration.c b/migration/migration.c
> index 353f272..5447cab 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1158,21 +1158,6 @@ void migrate_del_blocker(Error *reason)
>      migration_blockers = g_slist_remove(migration_blockers, reason);
>  }
>  
> -int check_migratable(Object *obj, Error **err)
> -{
> -    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> -    if (only_migratable && dc->vmsd) {
> -        if (dc->vmsd->unmigratable) {
> -            error_setg(err, "Device %s is not migratable, but "
> -                       "--only-migratable was specified",
> -                       object_get_typename(obj));
> -            return -1;
> -        }
> -    }
> -
> -    return 0;
> -}
> -
>  void qmp_migrate_incoming(const char *uri, Error **errp)
>  {
>      Error *local_err = NULL;
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 03ae1bd..7421a67 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2480,3 +2480,13 @@ void vmstate_register_ram_global(MemoryRegion *mr)
>  {
>      vmstate_register_ram(mr, NULL);
>  }
> +
> +bool vmstate_device_is_migratable(const VMStateDescription *vmsd)
> +{
> +    if (only_migratable && vmsd) {
> +        if (vmsd->unmigratable) {
> +            return false;
> +        }
> +    }
> +    return true;
> +}

Here the name vmstate_device_is_migratable() let me think of "return
true if the device can migrate, false otherwise". However what it
actually does is mixed with "--only-migratable" parameter, say, when
without that parameter, all device will be getting "true" here, even
unmigratable devices...

Not sure whether it'll be nicer we do this:

bool vmstate_device_is_migratable(const VMStateDescription *vmsd)
{
    return !(vmsd & vmsd->unmigratable);
}

Then we can define check_migratable() as:

static int check_migratable(Object *obj, Error **err)
{
    DeviceClass *dc = DEVICE_GET_CLASS(obj);

    /* no check needed if --only-migratable not specified */
    if (!only_migratable) {
       return true;
    }

    if (!vmstate_device_is_migratable(dc->vmsd)) {
        error_setg(err, "Device %s is not migratable, but "
                   "--only-migratable was specified",
                   object_get_typename(obj));
        return -1;
    }

    return 0;
}

Thanks,

> diff --git a/stubs/vmstate.c b/stubs/vmstate.c
> index 6d52f29..5af824b 100644
> --- a/stubs/vmstate.c
> +++ b/stubs/vmstate.c
> @@ -1,7 +1,6 @@
>  #include "qemu/osdep.h"
>  #include "qemu-common.h"
>  #include "migration/vmstate.h"
> -#include "migration/migration.h"
>  
>  const VMStateDescription vmstate_dummy = {};
>  
> @@ -21,7 +20,7 @@ void vmstate_unregister(DeviceState *dev,
>  {
>  }
>  
> -int check_migratable(Object *obj, Error **err)
> +bool vmstate_device_is_migratable(const VMStateDescription *vmsd)
>  {
> -    return 0;
> +    return true;
>  }
> -- 
> 2.9.3
> 

-- 
Peter Xu