[Qemu-devel] [PATCH 19/18] Introduce "xen-load-devices-state"

[Wen Congyang]

Introduce a "xen-load-devices-state" QAPI command that can be used to load
the state of all devices, but not the RAM or the block devices of the
VM.

We only have hmp commands savevm/loadvm, and qmp commands
xen-save-devices-state.

We use this new command for COLO:
1. suspend both primay vm and secondary vm
2. sync the state
3. resume both primary vm and secondary vm

In such case, we need to update all devices's state in any time.

Signed-off-by: Wen Congyang <address@hidden>
Cc: qemu-devl <address@hidden>
Cc: Stefano Stabellini <address@hidden>
Cc: Paolo Bonzini <address@hidden>
---
 qapi-schema.json | 18 ++++++++++++++++++
 qmp-commands.hx  | 27 +++++++++++++++++++++++++++
 savevm.c         | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)

diff --git a/qapi-schema.json b/qapi-schema.json
index 391356f..c569856 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4689,3 +4689,21 @@
               'btn'     : 'InputBtnEvent',
               'rel'     : 'InputMoveEvent',
               'abs'     : 'InputMoveEvent' } }
+
+##
+# @xen-load-devices-state:
+#
+# Load the state of all devices from file. The RAM and the block devices
+# of the VM are not loaded by this command.
+#
+# @filename: the file to load the state of the devices from as binary
+# data. See xen-save-devices-state.txt for a description of the binary
+# format.
+#
+# Returns: Nothing on success
+#          If @filename cannot be opened, OpenFileFailed
+#          If an I/O error occurs while reading the file, IOError
+#
+# Since: 2.0
+##
+{ 'command': 'xen-load-devices-state', 'data': {'filename': 'str'} }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index ed3ab92..b796be5 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -586,6 +586,33 @@ Example:
 EQMP
 
     {
+        .name       = "xen-load-devices-state",
+        .args_type  = "filename:F",
+        .mhandler.cmd_new = qmp_marshal_input_xen_load_devices_state,
+    },
+
+SQMP
+xen-load-devices-state
+-------
+
+Load the state of all devices from file. The RAM and the block devices
+of the VM are not loaded by this command.
+
+Arguments:
+
+- "filename": the file to load the state of the devices from as binary
+data. See xen-save-devices-state.txt for a description of the binary
+format.
+
+Example:
+
+-> { "execute": "xen-load-devices-state",
+     "arguments": { "filename": "/tmp/resume" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "xen-set-global-dirty-log",
         .args_type  = "enable:b",
         .mhandler.cmd_new = qmp_marshal_input_xen_set_global_dirty_log,
diff --git a/savevm.c b/savevm.c
index 22123be..3ebc01f 100644
--- a/savevm.c
+++ b/savevm.c
@@ -41,6 +41,7 @@
 #include "qemu/iov.h"
 #include "block/snapshot.h"
 #include "block/qapi.h"
+#include "hw/xen/xen.h"
 
 #define SELF_ANNOUNCE_ROUNDS 5
 
@@ -802,6 +803,14 @@ int qemu_loadvm_state(QEMUFile *f)
                 goto out;
             }
 
+            /* Validate if it is a device's state */
+            if (xen_enabled() && se->is_ram) {
+                fprintf(stderr, "loadvm: %s RAM loading not allowed on Xen\n",
+                        idstr);
+                ret = -EINVAL;
+                goto out;
+            }
+
             /* Add entry */
             le = g_malloc0(sizeof(*le));
 
@@ -1027,6 +1036,33 @@ void qmp_xen_save_devices_state(const char *filename, 
Error **errp)
     }
 }
 
+void qmp_xen_load_devices_state(const char *filename, Error **errp)
+{
+    QEMUFile *f;
+    int saved_vm_running;
+    int ret;
+
+    saved_vm_running = runstate_is_running();
+    vm_stop(RUN_STATE_RESTORE_VM);
+
+    f = qemu_fopen(filename, "rb");
+    if (!f) {
+        error_setg_file_open(errp, errno, filename);
+        goto out;
+    }
+
+    ret = qemu_loadvm_state(f);
+    qemu_fclose(f);
+    if (ret < 0) {
+        error_set(errp, QERR_IO_ERROR);
+    }
+
+out:
+    if (saved_vm_running) {
+        vm_start();
+    }
+}
+
 int load_vmstate(const char *name)
 {
     BlockDriverState *bs, *bs_vm_state;
-- 
1.9.3