[RFC Patch v3 23/22] Introduce "xen-load-devices-state"

[Wen Congyang <wency@cn.fujitsu.com>]

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.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 qapi-schema.json |  18 ++++++++
 qmp-commands.hx  |  27 ++++++++++++
 savevm.c         | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 171 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..c6aa502 100644
--- a/savevm.c
+++ b/savevm.c
@@ -863,6 +863,105 @@ out:
     return ret;
 }
 
+static int qemu_load_devices_state(QEMUFile *f)
+{
+    uint8_t section_type;
+    unsigned int v;
+    int ret;
+
+    if (qemu_savevm_state_blocked(NULL)) {
+        return -EINVAL;
+    }
+
+    v = qemu_get_be32(f);
+    if (v != QEMU_VM_FILE_MAGIC) {
+        return -EINVAL;
+    }
+
+    v = qemu_get_be32(f);
+    if (v == QEMU_VM_FILE_VERSION_COMPAT) {
+        fprintf(stderr, "SaveVM v2 format is obsolete and don't work anymore\n");
+        return -ENOTSUP;
+    }
+    if (v != QEMU_VM_FILE_VERSION) {
+        return -ENOTSUP;
+    }
+
+    while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
+        uint32_t instance_id, version_id, section_id;
+        SaveStateEntry *se;
+        char idstr[257];
+        int len;
+
+        switch (section_type) {
+        case QEMU_VM_SECTION_FULL:
+            /* Read section start */
+            section_id = qemu_get_be32(f);
+            len = qemu_get_byte(f);
+            qemu_get_buffer(f, (uint8_t *)idstr, len);
+            idstr[len] = 0;
+            instance_id = qemu_get_be32(f);
+            version_id = qemu_get_be32(f);
+
+            /* Find savevm section */
+            se = find_se(idstr, instance_id);
+            if (se == NULL) {
+                fprintf(stderr, "Unknown savevm section or instance '%s' %d\n",
+                        idstr, instance_id);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            /* Validate version */
+            if (version_id > se->version_id) {
+                fprintf(stderr, "loadvm: unsupported version %d for '%s' v%d\n",
+                        version_id, idstr, se->version_id);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            /* Validate if it is a device's state */
+            if (se->is_ram) {
+                fprintf(stderr, "loadvm: %s is not devices state\n", idstr);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            ret = vmstate_load(f, se, version_id);
+            if (ret < 0) {
+                fprintf(stderr, "qemu: warning: error while loading state for instance 0x%x of device '%s'\n",
+                        instance_id, idstr);
+                goto out;
+            }
+            break;
+        case QEMU_VM_SECTION_START:
+        case QEMU_VM_SECTION_PART:
+        case QEMU_VM_SECTION_END:
+            /*
+             * The file is saved by the command xen-save-devices-state,
+             * So it should not contain section start/part/end.
+             */
+        default:
+            fprintf(stderr, "Unknown savevm section type %d\n", section_type);
+            ret = -EINVAL;
+            goto out;
+        }
+    }
+
+    cpu_synchronize_all_post_init();
+
+    ret = 0;
+
+out:
+    if (ret == 0) {
+        if (qemu_file_get_error(f)) {
+            ret = -EIO;
+        }
+    }
+
+    return ret;
+}
+
 static BlockDriverState *find_vmstate_bs(void)
 {
     BlockDriverState *bs = NULL;
@@ -1027,6 +1126,33 @@ 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_load_devices_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;
-- 
1.9.0