virtio-scsi has been supported in qemu since 2012, and it is superior
in every respect to virtio-blk. There's no reason to still be using
virtio-blk.
virtio-scsi support was initially added in 2012
(commit 0c0a7d0d86).
You can still use virtio-blk using the (deprecated) iface parameter,
but don't do that in new code.