vfio/migration: Multifd setup/cleanup functions and associated VFIOMultifd

Add multifd setup/cleanup functions and an associated VFIOMultifd data
structure that will contain most of the receive-side data together
with its init/cleanup methods.

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/c0520523053b1087787152ddf2163257d3030be0.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/migration-multifd.c

@@ -32,8 +32,52 @@ typedef struct VFIODeviceStatePacket {
     uint8_t data[0];
 } QEMU_PACKED VFIODeviceStatePacket;
 
+typedef struct VFIOMultifd {
+} VFIOMultifd;
+
+static VFIOMultifd *vfio_multifd_new(void)
+{
+    VFIOMultifd *multifd = g_new(VFIOMultifd, 1);
+
+    return multifd;
+}
+
+static void vfio_multifd_free(VFIOMultifd *multifd)
+{
+    g_free(multifd);
+}
+
+void vfio_multifd_cleanup(VFIODevice *vbasedev)
+{
+    VFIOMigration *migration = vbasedev->migration;
+
+    g_clear_pointer(&migration->multifd, vfio_multifd_free);
+}
+
 bool vfio_multifd_transfer_supported(void)
 {
     return multifd_device_state_supported() &&
         migrate_send_switchover_start();
 }
+
+bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev)
+{
+    return false;
+}
+
+bool vfio_multifd_setup(VFIODevice *vbasedev, bool alloc_multifd, Error **errp)
+{
+    VFIOMigration *migration = vbasedev->migration;
+
+    if (!vfio_multifd_transfer_enabled(vbasedev)) {
+        /* Nothing further to check or do */
+        return true;
+    }
+
+    if (alloc_multifd) {
+        assert(!migration->multifd);
+        migration->multifd = vfio_multifd_new();
+    }
+
+    return true;
+}

hw/vfio/migration-multifd.h

@@ -14,6 +14,10 @@
 
 #include "hw/vfio/vfio-common.h"
 
+bool vfio_multifd_setup(VFIODevice *vbasedev, bool alloc_multifd, Error **errp);
+void vfio_multifd_cleanup(VFIODevice *vbasedev);
+
 bool vfio_multifd_transfer_supported(void);
+bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev);
 
 #endif

include/hw/vfio/vfio-common.h

@@ -78,6 +78,8 @@ typedef struct VFIORegion {
     uint8_t nr; /* cache the region number for debug */
 } VFIORegion;
 
+typedef struct VFIOMultifd VFIOMultifd;
+
 typedef struct VFIOMigration {
     struct VFIODevice *vbasedev;
     VMChangeStateEntry *vm_state;
@@ -89,6 +91,7 @@ typedef struct VFIOMigration {
     uint64_t mig_flags;
     uint64_t precopy_init_size;
     uint64_t precopy_dirty_size;
+    VFIOMultifd *multifd;
     bool initial_data_sent;
 
     bool event_save_iterate_started;