vfio/migration: Multifd device state transfer support - config loading support

Load device config received via multifd using the existing machinery
behind vfio_load_device_config_state().

Also, make sure to process the relevant main migration channel flags.

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/5dbd3f3703ec1097da2cf82a7262233452146fee.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/migration-multifd.c

@@ -17,6 +17,7 @@
 #include "qemu/lockable.h"
 #include "qemu/main-loop.h"
 #include "qemu/thread.h"
+#include "io/channel-buffer.h"
 #include "migration/qemu-file.h"
 #include "migration-multifd.h"
 #include "trace.h"
@@ -193,10 +194,54 @@ bool vfio_multifd_load_state_buffer(void *opaque, char *data, size_t data_size,
 static bool vfio_load_bufs_thread_load_config(VFIODevice *vbasedev,
                                               Error **errp)
 {
-    error_setg(errp, "not yet there");
+    VFIOMigration *migration = vbasedev->migration;
+    VFIOMultifd *multifd = migration->multifd;
+    VFIOStateBuffer *lb;
+    g_autoptr(QIOChannelBuffer) bioc = NULL;
+    g_autoptr(QEMUFile) f_out = NULL, f_in = NULL;
+    uint64_t mig_header;
+    int ret;
+
+    assert(multifd->load_buf_idx == multifd->load_buf_idx_last);
+    lb = vfio_state_buffers_at(&multifd->load_bufs, multifd->load_buf_idx);
+    assert(lb->is_present);
+
+    bioc = qio_channel_buffer_new(lb->len);
+    qio_channel_set_name(QIO_CHANNEL(bioc), "vfio-device-config-load");
+
+    f_out = qemu_file_new_output(QIO_CHANNEL(bioc));
+    qemu_put_buffer(f_out, (uint8_t *)lb->data, lb->len);
+
+    ret = qemu_fflush(f_out);
+    if (ret) {
+        error_setg(errp, "%s: load config state flush failed: %d",
+                   vbasedev->name, ret);
         return false;
     }
 
+    qio_channel_io_seek(QIO_CHANNEL(bioc), 0, 0, NULL);
+    f_in = qemu_file_new_input(QIO_CHANNEL(bioc));
+
+    mig_header = qemu_get_be64(f_in);
+    if (mig_header != VFIO_MIG_FLAG_DEV_CONFIG_STATE) {
+        error_setg(errp, "%s: expected FLAG_DEV_CONFIG_STATE but got %" PRIx64,
+                   vbasedev->name, mig_header);
+        return false;
+    }
+
+    bql_lock();
+    ret = vfio_load_device_config_state(f_in, vbasedev);
+    bql_unlock();
+
+    if (ret < 0) {
+        error_setg(errp, "%s: vfio_load_device_config_state() failed: %d",
+                   vbasedev->name, ret);
+        return false;
+    }
+
+    return true;
+}
+
 static VFIOStateBuffer *vfio_load_state_buffer_get(VFIOMultifd *multifd)
 {
     VFIOStateBuffer *lb;

hw/vfio/migration.c

@@ -264,7 +264,7 @@ static int vfio_save_device_config_state(QEMUFile *f, void *opaque,
     return ret;
 }
 
-static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
+int vfio_load_device_config_state(QEMUFile *f, void *opaque)
 {
     VFIODevice *vbasedev = opaque;
     uint64_t data;
@@ -723,6 +723,13 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
         switch (data) {
         case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
         {
+            if (vfio_multifd_transfer_enabled(vbasedev)) {
+                error_report("%s: got DEV_CONFIG_STATE in main migration "
+                             "channel but doing multifd transfer",
+                             vbasedev->name);
+                return -EINVAL;
+            }
+
             return vfio_load_device_config_state(f, opaque);
         }
         case VFIO_MIG_FLAG_DEV_SETUP_STATE:

include/hw/vfio/vfio-common.h

@@ -298,6 +298,8 @@ void vfio_mig_add_bytes_transferred(unsigned long val);
 bool vfio_device_state_is_running(VFIODevice *vbasedev);
 bool vfio_device_state_is_precopy(VFIODevice *vbasedev);
 
+int vfio_load_device_config_state(QEMUFile *f, void *opaque);
+
 #ifdef CONFIG_LINUX
 int vfio_get_region_info(VFIODevice *vbasedev, int index,
                          struct vfio_region_info **info);