Bug 13229

There following kernel warning is printed during boot

[   18.370702] ------------[ cut here ]------------
[   18.382099] WARNING: CPU: 0 PID: 446 at drivers/gpu/drm/ttm/ttm_bo_vm.c:303 ttm_bo_vm_open+0x3c/0x4c
[   18.383267] Modules linked in:
[   18.383789] CPU: 0 PID: 446 Comm: Xorg Not tainted 4.19.19-yocto-standard #1
[   18.383964] Hardware name: Generic DT based system
[   18.384508] [<c021306c>] (unwind_backtrace) from [<c020d174>] (show_stack+0x20/0x24)
[   18.384719] [<c020d174>] (show_stack) from [<c09964a0>] (dump_stack+0x84/0xa4)
[   18.384904] [<c09964a0>] (dump_stack) from [<c0231dd0>] (__warn+0xe8/0x104)
[   18.385114] [<c0231dd0>] (__warn) from [<c0232180>] (warn_slowpath_null+0x4c/0x58)
[   18.385300] [<c0232180>] (warn_slowpath_null) from [<c072b408>] (ttm_bo_vm_open+0x3c/0x4c)
[   18.385499] [<c072b408>] (ttm_bo_vm_open) from [<c0230718>] (copy_process.part.3+0x13c4/0x17f0)
[   18.385703] [<c0230718>] (copy_process.part.3) from [<c0230ce8>] (_do_fork+0xc8/0x414)
[   18.385907] [<c0230ce8>] (_do_fork) from [<c0231154>] (sys_clone+0x30/0x38)
[   18.386108] [<c0231154>] (sys_clone) from [<c0201000>] (ret_fast_syscall+0x0/0x4c)
[   18.386308] Exception stack(0xde279fa8 to 0xde279ff0)
[   18.386477] 9fa0:                   b6ef7078 b6f03000 01200011 00000000 00000000 00000000
[   18.386672] 9fc0: b6ef7078 b6f03000 b6ef74d0 00000078 00000000 b6ef7010 0051b03d be9bc9fc
[   18.386857] 9fe0: 00000078 be9ba8a8 b6ad564d b6a7ac46
[   18.387096] ---[ end trace e8a5e15e3b7db8a9 ]---


This issue occurred after adding the Bochs VGA hardware (to enable graphics) in the qemuarm/qemuarm64 config files.  It does not appear to affect the functionality of graphics.