vfio/migration: Multifd device state transfer support - basic types

Add basic types and flags used by VFIO multifd device state transfer
support.

Since we'll be introducing a lot of multifd transfer specific code,
add a new file migration-multifd.c to home it, wired into main VFIO
migration code (migration.c) via migration-multifd.h header file.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/4eedd529e6617f80f3d6a66d7268a0db2bc173fa.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/meson.build

@@ -5,6 +5,7 @@ vfio_ss.add(files(
   'container-base.c',
   'container.c',
   'migration.c',
+  'migration-multifd.c',
   'cpr.c',
 ))
 vfio_ss.add(when: 'CONFIG_PSERIES', if_true: files('spapr.c'))

hw/vfio/migration-multifd.c

@@ -0,0 +1,33 @@
+/*
+ * Multifd VFIO migration
+ *
+ * Copyright (C) 2024,2025 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/vfio/vfio-common.h"
+#include "migration/misc.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+#include "qemu/lockable.h"
+#include "qemu/main-loop.h"
+#include "qemu/thread.h"
+#include "migration/qemu-file.h"
+#include "migration-multifd.h"
+#include "trace.h"
+
+#define VFIO_DEVICE_STATE_CONFIG_STATE (1)
+
+#define VFIO_DEVICE_STATE_PACKET_VER_CURRENT (0)
+
+typedef struct VFIODeviceStatePacket {
+    uint32_t version;
+    uint32_t idx;
+    uint32_t flags;
+    uint8_t data[0];
+} QEMU_PACKED VFIODeviceStatePacket;

hw/vfio/migration-multifd.h

@@ -0,0 +1,17 @@
+/*
+ * Multifd VFIO migration
+ *
+ * Copyright (C) 2024,2025 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_VFIO_MIGRATION_MULTIFD_H
+#define HW_VFIO_MIGRATION_MULTIFD_H
+
+#include "hw/vfio/vfio-common.h"
+
+#endif

hw/vfio/migration.c

@@ -23,6 +23,7 @@
 #include "migration/qemu-file.h"
 #include "migration/register.h"
 #include "migration/blocker.h"
+#include "migration-multifd.h"
 #include "qapi/error.h"
 #include "qapi/qapi-events-vfio.h"
 #include "exec/ramlist.h"