[Qemu-devel] [PATCH v2 0.15 1/4] add support for machine models to specify their migration format

[Paolo Bonzini <pbonzini@redhat.com>]

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>
---
 cpu-common.h  |    3 ---
 hw/boards.h   |    1 +
 qemu-common.h |    3 +++
 savevm.c      |   16 ++++++++++++++--
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/cpu-common.h b/cpu-common.h
index 44b04b3..8c61b18 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 ba55719..24330be 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -91,6 +91,9 @@ static inline char *realpath(const char *path, char *resolved_path)
 }
 #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..3049aa1 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"
@@ -1461,6 +1462,16 @@ bool qemu_savevm_state_blocked(Monitor *mon)
     return false;
 }
 
+static inline int qemu_current_migration_format(void)
+{
+    if (current_machine->migration_format) {
+        return current_machine->migration_format;
+    }
+
+    /* No format specified, default to the latest.  */
+    return QEMU_VM_FILE_VERSION;
+}
+
 int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
                             int shared)
 {
@@ -1474,7 +1484,7 @@ 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, qemu_current_migration_format());
 
     QTAILQ_FOREACH(se, &savevm_handlers, entry) {
         int len;
@@ -1747,8 +1757,10 @@ 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 != qemu_current_migration_format()) {
+        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;
-- 
1.7.6