anchor.diff:                (return-from virtio::virtio-gpu-register nil)))
             (setf (virtio-gpu-scanout gpu) pmode
                   (virtio-gpu-width gpu) width
  -                (virtio-gpu-height gpu) height)
  +                (virtio-gpu-height gpu) height
  +                (virtio-gpu-framebuffer gpu) framebuffer-dma-buffer)
             (sup::video-set-framebuffer framebuffer-phys width height
                                         (* width 4) :x8r8g8b8
                                         :damage-fn
  
positive.code:         (when (not successp)
            (sup:debug-print-line "virtio-gpu: Unable to create framebuffer resource: " error)
            (return-from virtio::virtio-gpu-register nil)))
        (let* ((framebuffer-size (* width height 4))
               (n-framebuffer-pages (ceiling framebuffer-size sup::+4k-page-size+))
               (framebuffer-frames (sup::allocate-physical-pages n-framebuffer-pages)))
          (when (not framebuffer-frames)
            (sup:debug-print-line "virtio-gpu: Unable to allocate framebuffer memory")
            (return-from virtio::virtio-gpu-register nil))
          (let ((framebuffer-phys (* framebuffer-frames sup::+4k-page-size+)))
            (sup:debug-print-line "virtio-gpu: Framebuffer at " framebuffer-phys)
            ;; Clear framebuffer.
            (sys.int::%fill-words (sup::convert-to-pmap-address framebuffer-phys)
                                  0
                                  (truncate framebuffer-size 8))
            ;; Attach backing store to framebuffer resource.
  
negative.code:            #:virtio-gpu-scanout
             #:virtio-gpu-width
             #:virtio-gpu-height
             #:virtio-gpu-framebuffer
             #:virtio-gpu-virgl-p
             #:virtio-gpu-virgl-data
  
  