Trusty Server (daily image 2014-01-15)
Kernel: 3.13.0-3.18-generic 64bit
Booting a VM which is set to use cirrus graphics there seems to (still) be a problem with the framebuffers. The kernel has a special KMS module which also has a framebuffer interface. During boot plymouth likely keeps the fb open which the kernel tries to replace the generic FB with the special one (and fails). Symptom is a system which seems to hang on boot when looking at the graphical console.
[ 7.140598] checking generic (fc000000 160000) vs hw (fc000000 2000000)
[ 7.140603] fb: conflicting fb hw usage cirrusdrmfb vs simple - removing generic driver
[ 7.140650] Console: switching to colour dummy device 80x25
[ 7.144410] [drm:cirrus_vram_init] *ERROR* can't reserve VRAM
[ 7.144422] cirrus 0000:00:02.0: Fatal error during GPU init: -6
[ 7.144426] Trying to free nonexistent resource <00000000febf4000-00000000febf4fff>
[ 7.144431] Trying to free nonexistent resource <00000000fc000000-00000000fc3fffff>
[ 8.254229] systemd-udevd[302]: Failed to apply ACL on /dev/dri/card0: No such file or directory
Simple-framebuffer has now been disabled for X86.