vfio: Introduce a new header file for external migration services

The migration core subsystem makes use of the VFIO migration API to
collect statistics on the number of bytes transferred. These services
are declared in "hw/vfio/vfio-common.h" which also contains VFIO
internal declarations. Move the migration declarations into a new
header file "hw/vfio/vfio-migration.h" to reduce the exposure of VFIO
internals.

While at it, use a 'vfio_migration_' prefix for these services.

To be noted, vfio_migration_add_bytes_transferred() is a VFIO
migration internal service which we will be moved in the subsequent
patches.

Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Reviewed-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/qemu-devel/20250326075122.1299361-4-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/migration-multifd.c

@@ -11,6 +11,7 @@
 
 #include "qemu/osdep.h"
 #include "hw/vfio/vfio-common.h"
+#include "hw/vfio/vfio-migration.h"
 #include "migration/misc.h"
 #include "qapi/error.h"
 #include "qemu/bswap.h"
@@ -575,7 +576,7 @@ vfio_save_complete_precopy_thread_config_state(VFIODevice *vbasedev,
         return false;
     }
 
-    vfio_mig_add_bytes_transferred(packet_len);
+    vfio_migration_add_bytes_transferred(packet_len);
 
     return true;
 }
@@ -645,7 +646,7 @@ vfio_multifd_save_complete_precopy_thread(SaveLiveCompletePrecopyThreadData *d,
             goto thread_exit;
         }
 
-        vfio_mig_add_bytes_transferred(packet_size);
+        vfio_migration_add_bytes_transferred(packet_size);
     }
 
     if (!vfio_save_complete_precopy_thread_config_state(vbasedev,

hw/vfio/migration.c

@@ -17,6 +17,7 @@
 
 #include "system/runstate.h"
 #include "hw/vfio/vfio-common.h"
+#include "hw/vfio/vfio-migration.h"
 #include "migration/misc.h"
 #include "migration/savevm.h"
 #include "migration/vmstate.h"
@@ -373,7 +374,7 @@ static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration)
     qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
     qemu_put_be64(f, data_size);
     qemu_put_buffer(f, migration->data_buffer, data_size);
-    vfio_mig_add_bytes_transferred(data_size);
+    vfio_migration_add_bytes_transferred(data_size);
 
     trace_vfio_save_block(migration->vbasedev->name, data_size);
 
@@ -1047,22 +1048,22 @@ static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
 
 /* ---------------------------------------------------------------------- */
 
-int64_t vfio_mig_bytes_transferred(void)
+int64_t vfio_migration_bytes_transferred(void)
 {
     return MIN(qatomic_read(&bytes_transferred), INT64_MAX);
 }
 
-void vfio_mig_reset_bytes_transferred(void)
+void vfio_migration_reset_bytes_transferred(void)
 {
     qatomic_set(&bytes_transferred, 0);
 }
 
-void vfio_mig_add_bytes_transferred(unsigned long val)
+void vfio_migration_add_bytes_transferred(unsigned long val)
 {
     qatomic_add(&bytes_transferred, val);
 }
 
-bool vfio_mig_active(void)
+bool vfio_migration_active(void)
 {
     VFIODevice *vbasedev;
 

include/hw/vfio/vfio-common.h

@@ -290,13 +290,10 @@ extern VFIODeviceList vfio_device_list;
 extern const MemoryListener vfio_memory_listener;
 extern int vfio_kvm_device_fd;
 
-bool vfio_mig_active(void);
 int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp);
 void vfio_unblock_multiple_devices_migration(void);
 bool vfio_viommu_preset(VFIODevice *vbasedev);
-int64_t vfio_mig_bytes_transferred(void);
-void vfio_mig_reset_bytes_transferred(void);
-void vfio_mig_add_bytes_transferred(unsigned long val);
+void vfio_migration_add_bytes_transferred(unsigned long val);
 bool vfio_device_state_is_running(VFIODevice *vbasedev);
 bool vfio_device_state_is_precopy(VFIODevice *vbasedev);
 

include/hw/vfio/vfio-migration.h

@@ -0,0 +1,16 @@
+/*
+ * VFIO migration interface
+ *
+ * Copyright Red Hat, Inc. 2025
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_VFIO_VFIO_MIGRATION_H
+#define HW_VFIO_VFIO_MIGRATION_H
+
+bool vfio_migration_active(void);
+int64_t vfio_migration_bytes_transferred(void);
+void vfio_migration_reset_bytes_transferred(void);
+
+#endif /* HW_VFIO_VFIO_MIGRATION_H */

migration/target.c

@@ -11,21 +11,21 @@
 #include CONFIG_DEVICES
 
 #ifdef CONFIG_VFIO
-#include "hw/vfio/vfio-common.h"
+#include "hw/vfio/vfio-migration.h"
 #endif
 
 #ifdef CONFIG_VFIO
 void migration_populate_vfio_info(MigrationInfo *info)
 {
-    if (vfio_mig_active()) {
+    if (vfio_migration_active()) {
         info->vfio = g_malloc0(sizeof(*info->vfio));
-        info->vfio->transferred = vfio_mig_bytes_transferred();
+        info->vfio->transferred = vfio_migration_bytes_transferred();
     }
 }
 
 void migration_reset_vfio_bytes_transferred(void)
 {
-    vfio_mig_reset_bytes_transferred();
+    vfio_migration_reset_bytes_transferred();
 }
 #else
 void migration_populate_vfio_info(MigrationInfo *info)