[Qemu-devel] Re: [PATCH RFC] Mark a device as non-migratable

[Anthony Liguori]

On 06/15/2010 11:16 AM, Cam Macdonell wrote:
> How does this look for marking the device as non-migratable?  It adds a field
> 'no_migrate' to the SaveStateEntry and tests for it in vmstate_save.  This would
> replace anything that touches memory.
>
> Cam
>
> ---
>   hw/hw.h  |    1 +
>   savevm.c |   32 +++++++++++++++++++++++++++++---
>   2 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/hw/hw.h b/hw/hw.h
> index d78d814..7c93f08 100644
> --- a/hw/hw.h
> +++ b/hw/hw.h
> @@ -263,6 +263,7 @@ int register_savevm_live(const char *idstr,
>                            void *opaque);
>
>   void unregister_savevm(const char *idstr, void *opaque);
> +void mark_no_migrate(const char *idstr, void *opaque);
>    

I'm not thrilled with the name but the functionality is spot on.  I lack 
the creativity to offer a better name suggestion :-)

Regards,

Anthony Liguori

>   typedef void QEMUResetHandler(void *opaque);
>
> diff --git a/savevm.c b/savevm.c
> index 017695b..2642a9c 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -1023,6 +1023,7 @@ typedef struct SaveStateEntry {
>       LoadStateHandler *load_state;
>       const VMStateDescription *vmsd;
>       void *opaque;
> +    int no_migrate;
>   } SaveStateEntry;
>
>
> @@ -1069,6 +1070,7 @@ int register_savevm_live(const char *idstr,
>       se->load_state = load_state;
>       se->opaque = opaque;
>       se->vmsd = NULL;
> +    se->no_migrate = 0;
>
>       if (instance_id == -1) {
>           se->instance_id = calculate_new_instance_id(idstr);
> @@ -1103,6 +1105,19 @@ void unregister_savevm(const char *idstr, void *opaque)
>       }
>   }
>
> +/* mark a device as not to be migrated, that is the device should be
> +   unplugged before migration */
> +void mark_no_migrate(const char *idstr, void *opaque)
> +{
> +    SaveStateEntry *se;
> +
> +    QTAILQ_FOREACH(se,&savevm_handlers, entry) {
> +        if (strcmp(se->idstr, idstr) == 0&&  se->opaque == opaque) {
> +            se->no_migrate = 1;
> +        }
> +    }
> +}
> +
>   int vmstate_register_with_alias_id(int instance_id,
>                                      const VMStateDescription *vmsd,
>                                      void *opaque, int alias_id,
> @@ -1277,13 +1292,19 @@ static int vmstate_load(QEMUFile *f, SaveStateEntry 
> *se, int version_id)
>       return vmstate_load_state(f, se->vmsd, se->opaque, version_id);
>   }
>
> -static void vmstate_save(QEMUFile *f, SaveStateEntry *se)
> +static int vmstate_save(QEMUFile *f, SaveStateEntry *se)
>   {
> +    if (se->no_migrate) {
> +        return -1;
> +    }
> +
>       if (!se->vmsd) {         /* Old style */
>           se->save_state(f, se->opaque);
> -        return;
> +        return 0;
>       }
>       vmstate_save_state(f,se->vmsd, se->opaque);
> +
> +    return 0;
>   }
>
>   #define QEMU_VM_FILE_MAGIC           0x5145564d
> @@ -1377,6 +1398,7 @@ int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f)
>   int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f)
>   {
>       SaveStateEntry *se;
> +    int r;
>
>       cpu_synchronize_all_states();
>
> @@ -1409,7 +1431,11 @@ int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f)
>           qemu_put_be32(f, se->instance_id);
>           qemu_put_be32(f, se->version_id);
>
> -        vmstate_save(f, se);
> +        r = vmstate_save(f, se);
> +        if (r<  0) {
> +            monitor_printf(mon, "cannot migrate with device '%s'\n", 
> se->idstr);
> +            return r;
> +        }
>       }
>
>       qemu_put_byte(f, QEMU_VM_EOF);
>