@Trantor
I believe this should get VIRTIO disk to work.
edit the following file:
drivers/block/virtio_blk.c
on line 758 in the latest posted kernel source change:
virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
to
virtblk_name_format("sd", index, vblk->disk->disk_name, DISK_NAME_LEN);
then synology should be able to detect virtio disks. if you can try this to see if it works or help assist me in getting a working .config i would greatly appreciate it.