[Qemu-devel] [PATCH v2 07/43] Migration commands

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Create QEMU_VM_COMMAND section type for sending commands from
source to destination.  These commands are not intended to convey
guest state but to control the migration process.

For use in postcopy.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/migration/migration.h |  1 +
 include/sysemu/sysemu.h       |  7 +++++
 savevm.c                      | 62 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 8a36255..e23947a 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -33,6 +33,7 @@
 #define QEMU_VM_SECTION_END          0x03
 #define QEMU_VM_SECTION_FULL         0x04
 #define QEMU_VM_SUBSECTION           0x05
+#define QEMU_VM_COMMAND              0x06
 
 struct MigrationParams {
     bool blk;
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index d8539fd..66821eb 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -81,6 +81,13 @@ void do_info_snapshots(Monitor *mon, const QDict *qdict);
 
 void qemu_announce_self(void);
 
+/* Subcommands for QEMU_VM_COMMAND */
+enum qemu_vm_cmd {
+    QEMU_VM_CMD_INVALID = 0,   /* Must be 0 */
+
+    QEMU_VM_CMD_AFTERLASTVALID
+};
+
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_state_begin(QEMUFile *f,
                              const MigrationParams *params);
diff --git a/savevm.c b/savevm.c
index a0c3b40..8a1f5f1 100644
--- a/savevm.c
+++ b/savevm.c
@@ -592,6 +592,25 @@ static void vmstate_save(QEMUFile *f, SaveStateEntry *se)
     vmstate_save_state(f, se->vmsd, se->opaque);
 }
 
+
+/* Send a 'QEMU_VM_COMMAND' type element with the command
+ * and associated data.
+ */
+void qemu_savevm_command_send(QEMUFile *f,
+                              enum qemu_vm_cmd command,
+                              uint16_t len,
+                              uint8_t *data)
+{
+    uint32_t tmp = (uint16_t)command;
+    qemu_put_byte(f, QEMU_VM_COMMAND);
+    qemu_put_be16(f, tmp);
+    qemu_put_be16(f, len);
+    if (len) {
+        qemu_put_buffer(f, data, len);
+    }
+    qemu_fflush(f);
+}
+
 bool qemu_savevm_state_blocked(Error **errp)
 {
     SaveStateEntry *se;
@@ -881,6 +900,43 @@ static SaveStateEntry *find_se(const char *idstr, int instance_id)
     return NULL;
 }
 
+static int loadvm_process_command_simple_lencheck(const char *name,
+                                                  unsigned int actual,
+                                                  unsigned int expected)
+{
+    if (actual != expected) {
+        error_report("%s received with bad length - expecting %d, got %d",
+                     name, expected, actual);
+        return -1;
+    }
+
+    return 0;
+}
+
+/*
+ * Process an incoming 'QEMU_VM_COMMAND'
+ * negative return on error (will issue error message)
+ */
+static int loadvm_process_command(QEMUFile *f)
+{
+    uint16_t com;
+    uint16_t len;
+    uint32_t tmp32;
+
+    com = qemu_get_be16(f);
+    len = qemu_get_be16(f);
+
+    /* fprintf(stderr,"loadvm_process_command: com=0x%x len=%d\n", com,len); */
+    switch (com) {
+
+    default:
+        error_report("VM_COMMAND 0x%x unknown (len 0x%x)", com, len);
+        return -1;
+    }
+
+    return 0;
+}
+
 typedef struct LoadStateEntry {
     QLIST_ENTRY(LoadStateEntry) entry;
     SaveStateEntry *se;
@@ -987,6 +1043,12 @@ int qemu_loadvm_state(QEMUFile *f)
                 goto out;
             }
             break;
+        case QEMU_VM_COMMAND:
+            ret = loadvm_process_command(f);
+            if (ret < 0) {
+                goto out;
+            }
+            break;
         default:
             fprintf(stderr, "Unknown savevm section type %d\n", section_type);
             ret = -EINVAL;
-- 
1.9.3