anchor.diff:            (sys.int::memref-unsigned-byte-32 (+ addr +virtio-gpu-ctrl-hdr-fence-id+) 0) fence-id
             (sys.int::memref-unsigned-byte-32 (+ addr +virtio-gpu-ctrl-hdr-ctx-id+) 0) ctx-id)))
   
  -(defun virtio-gpu-issue-command (gpu command-length response-length &optional in-unsafe-context-p)
  +(defun virtio-gpu-issue-command (gpu command-length response-length)
     (let* ((req-phys (virtio-gpu-request-phys gpu))
            (dev (virtio-gpu-virtio-device gpu))
            (vq (virtio-virtqueue dev +virtio-gpu-controlq+))
  
positive.code:           (t
             (values nil resp-type)))))
  
  (defun virtio-gpu-irq-handler (gpu)
    (latch-trigger (virtio-gpu-irq-latch gpu)))
  
  (defun virtio-gpu-dirty (gpu x y w h in-unsafe-context-p)
    ;; Issue commands to update the framebuffer and to flush the scanout.
    (virtio-gpu-configure-command gpu
                                  +virtio-gpu-cmd-transfer-to-host-2d+
                                  0
  
negative.code:     (when (not (virtio-configure-virtqueues device 2))
        (setf (virtio-device-status device) +virtio-status-failed+)
        (return-from virtio-gpu-register nil))
      ;; Configuration complete, go to OK mode.
      (setf (virtio-device-status device) (logior +virtio-status-acknowledge+
                                                  +virtio-status-driver+
  