[Qemu-devel] [PULL 2/2] Introduce "xen-load-devices-state"

[Stefano Stabellini <sstabellini@kernel.org>]

From: 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.

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

We use this new command for COLO:
1. suspend both primary 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' state in any time.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
---
 migration/savevm.c | 37 +++++++++++++++++++++++++++++++++++++
 qapi-schema.json   | 14 ++++++++++++++
 qmp-commands.hx    | 27 +++++++++++++++++++++++++++
 3 files changed, 78 insertions(+)

diff --git a/migration/savevm.c b/migration/savevm.c
index 6c21231..ae2ef8b 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -31,6 +31,7 @@
 #include "hw/boards.h"
 #include "hw/hw.h"
 #include "hw/qdev.h"
+#include "hw/xen/xen.h"
 #include "net/net.h"
 #include "monitor/monitor.h"
 #include "sysemu/sysemu.h"
@@ -1754,6 +1755,12 @@ qemu_loadvm_section_start_full(QEMUFile *f, MigrationIncomingState *mis)
         return -EINVAL;
     }
 
+    /* Validate if it is a device's state */
+    if (xen_enabled() && se->is_ram) {
+        error_report("loadvm: %s RAM loading not allowed on Xen", idstr);
+        return -EINVAL;
+    }
+
     /* Add entry */
     le = g_malloc0(sizeof(*le));
 
@@ -2064,6 +2071,36 @@ void qmp_xen_save_devices_state(const char *filename, Error **errp)
     }
 }
 
+void qmp_xen_load_devices_state(const char *filename, Error **errp)
+{
+    QEMUFile *f;
+    QIOChannelFile *ioc;
+    int ret;
+
+    /* Guest must be paused before loading the device state; the RAM state
+     * will already have been loaded by xc
+     */
+    if (runstate_is_running()) {
+        error_setg(errp, "Cannot update device state while vm is running");
+        return;
+    }
+    vm_stop(RUN_STATE_RESTORE_VM);
+
+    ioc = qio_channel_file_new_path(filename, O_RDONLY | O_BINARY, 0, errp);
+    if (!ioc) {
+        return;
+    }
+    f = qemu_fopen_channel_input(QIO_CHANNEL(ioc));
+
+    migration_incoming_state_new(f);
+    ret = qemu_loadvm_state(f);
+    qemu_fclose(f);
+    if (ret < 0) {
+        error_setg(errp, QERR_IO_ERROR);
+    }
+    migration_incoming_state_destroy();
+}
+
 int load_vmstate(const char *name)
 {
     BlockDriverState *bs, *bs_vm_state;
diff --git a/qapi-schema.json b/qapi-schema.json
index 8483bdf..48c3a6f 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4201,6 +4201,20 @@
   'data': [ 'none', 'record', 'play' ] }
 
 ##
+# @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.
+#
+# Since: 2.7
+##
+{ 'command': 'xen-load-devices-state', 'data': {'filename': 'str'} }
+
+##
 # @GICCapability:
 #
 # The struct describes capability for a specific GIC (Generic
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 28801a2..780e7f2 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -587,6 +587,33 @@ Example:
 EQMP
 
     {
+        .name       = "xen-load-devices-state",
+        .args_type  = "filename:F",
+        .mhandler.cmd_new = qmp_marshal_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_xen_set_global_dirty_log,
-- 
1.9.1