Re: [Qemu-devel] [RFC PATCH 1/4] add support for machine models to specify their migration format

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 30, 2011 at 05:46:14PM +0200, Paolo Bonzini wrote:
> We need to provide a new migration format, and not break migration
> in old machine models.  So add a migration_format field to QEMUMachine.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Should not machine describe guest behaviour?
It seems that a flag to the migrate/save command to control format
would be better - this way the same machine can
migrate to different formats.

> ---
>  cpu-common.h  |    3 ---
>  hw/boards.h   |    1 +
>  qemu-common.h |    3 +++
>  savevm.c      |    7 +++++--
>  4 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/cpu-common.h b/cpu-common.h
> index b027e43..8c06dbb 100644
> --- a/cpu-common.h
> +++ b/cpu-common.h
> @@ -26,9 +26,6 @@ enum device_endian {
>      DEVICE_LITTLE_ENDIAN,
>  };
>  
> -/* address in the RAM (different from a physical address) */
> -typedef unsigned long ram_addr_t;
> -
>  /* memory API */
>  
>  typedef void CPUWriteMemoryFunc(void *opaque, target_phys_addr_t addr, uint32_t value);
> diff --git a/hw/boards.h b/hw/boards.h
> index 716fd7b..560dbaf 100644
> --- a/hw/boards.h
> +++ b/hw/boards.h
> @@ -19,6 +19,7 @@ typedef struct QEMUMachine {
>      QEMUMachineInitFunc *init;
>      int use_scsi;
>      int max_cpus;
> +    unsigned migration_format;
>      unsigned int no_serial:1,
>          no_parallel:1,
>          use_virtcon:1,
> diff --git a/qemu-common.h b/qemu-common.h
> index 109498d..550fe2c 100644
> --- a/qemu-common.h
> +++ b/qemu-common.h
> @@ -119,6 +119,9 @@ static inline char *realpath(const char *path, char *resolved_path)
>  #define PRIo64 "I64o"
>  #endif
>  
> +/* address in the RAM (different from a physical address) */
> +typedef unsigned long ram_addr_t;
> +
>  /* FIXME: Remove NEED_CPU_H.  */
>  #ifndef NEED_CPU_H
>  
> diff --git a/savevm.c b/savevm.c
> index 8139bc7..74e6e99 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -72,6 +72,7 @@
>  #include "qemu-common.h"
>  #include "hw/hw.h"
>  #include "hw/qdev.h"
> +#include "hw/boards.h"
>  #include "net.h"
>  #include "monitor.h"
>  #include "sysemu.h"
> @@ -1474,7 +1475,7 @@ int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
>      }
>      
>      qemu_put_be32(f, QEMU_VM_FILE_MAGIC);
> -    qemu_put_be32(f, QEMU_VM_FILE_VERSION);
> +    qemu_put_be32(f, current_machine->migration_format ?: QEMU_VM_FILE_VERSION);
>  
>      QTAILQ_FOREACH(se, &savevm_handlers, entry) {
>          int len;
> @@ -1747,8 +1748,10 @@ int qemu_loadvm_state(QEMUFile *f)
>          fprintf(stderr, "SaveVM v2 format is obsolete and don't work anymore\n");
>          return -ENOTSUP;
>      }
> -    if (v != QEMU_VM_FILE_VERSION)
> +    if (v != (current_machine->migration_format ?: QEMU_VM_FILE_VERSION)) {
> +        fprintf(stderr, "Mismatching SaveVM format v%d\n", v);
>          return -ENOTSUP;
> +    }
>  
>      while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
>          uint32_t instance_id, version_id, section_id;
> -- 
> 1.7.5.2
> 
>