[Qemu-devel] [PATCH v7 12/42] 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 +++++++
 migration/savevm.c            | 46 +++++++++++++++++++++++++++++++++++++++++++
 trace-events                  |  1 +
 4 files changed, 55 insertions(+)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 414c5cf..8adaa45 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -34,6 +34,7 @@
 #define QEMU_VM_SECTION_FULL         0x04
 #define QEMU_VM_SUBSECTION           0x05
 #define QEMU_VM_VMDESCRIPTION        0x06
+#define QEMU_VM_COMMAND              0x07
 #define QEMU_VM_SECTION_FOOTER       0x7e
 
 struct MigrationParams {
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 6dae2db..5869607 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -82,6 +82,11 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict);
 
 void qemu_announce_self(void);
 
+/* Subcommands for QEMU_VM_COMMAND */
+enum qemu_vm_cmd {
+    MIG_CMD_INVALID = 0,   /* Must be 0 */
+};
+
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_state_begin(QEMUFile *f,
                              const MigrationParams *params);
@@ -90,6 +95,8 @@ int qemu_savevm_state_iterate(QEMUFile *f);
 void qemu_savevm_state_complete_precopy(QEMUFile *f);
 void qemu_savevm_state_cancel(void);
 uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size);
+void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command,
+                              uint16_t len, uint8_t *data);
 int qemu_loadvm_state(QEMUFile *f);
 
 typedef enum DisplayType
diff --git a/migration/savevm.c b/migration/savevm.c
index f9168ac..7ce9d21 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -686,6 +686,23 @@ static bool check_section_footer(QEMUFile *f, SaveStateEntry *se)
     return true;
 }
 
+/* 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)
+{
+    qemu_put_byte(f, QEMU_VM_COMMAND);
+    qemu_put_be16(f, (uint16_t)command);
+    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;
@@ -982,6 +999,29 @@ static SaveStateEntry *find_se(const char *idstr, int instance_id)
     return NULL;
 }
 
+/*
+ * Process an incoming 'QEMU_VM_COMMAND'
+ * negative return on error (will issue error message)
+ */
+static int loadvm_process_command(QEMUFile *f)
+{
+    uint16_t cmd;
+    uint16_t len;
+
+    cmd = qemu_get_be16(f);
+    len = qemu_get_be16(f);
+
+    trace_loadvm_process_command(cmd, len);
+    switch (cmd) {
+
+    default:
+        error_report("VM_COMMAND 0x%x unknown (len 0x%x)", cmd, len);
+        return -1;
+    }
+
+    return 0;
+}
+
 struct LoadStateEntry {
     QLIST_ENTRY(LoadStateEntry) entry;
     SaveStateEntry *se;
@@ -1114,6 +1154,12 @@ 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:
             error_report("Unknown savevm section type %d", section_type);
             ret = -EINVAL;
diff --git a/trace-events b/trace-events
index d539528..73a65c3 100644
--- a/trace-events
+++ b/trace-events
@@ -1183,6 +1183,7 @@ virtio_gpu_fence_resp(uint64_t fence) "fence 0x%" PRIx64
 qemu_loadvm_state_section(unsigned int section_type) "%d"
 qemu_loadvm_state_section_partend(uint32_t section_id) "%u"
 qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr, uint32_t instance_id, uint32_t version_id) "%u(%s) %u %u"
+loadvm_process_command(uint16_t com, uint16_t len) "com=0x%x len=%d"
 savevm_section_start(const char *id, unsigned int section_id) "%s, section_id %u"
 savevm_section_end(const char *id, unsigned int section_id, int ret) "%s, section_id %u -> %d"
 savevm_state_begin(void) ""
-- 
2.4.3