------------[ cut here ]------------
bochs-drm 0000:00:01.0: [drm] vblank wait timed out on crtc 0
WARNING: drivers/gpu/drm/drm_vblank.c:1329 at drm_crtc_wait_one_vblank+0x31d/0x580 drivers/gpu/drm/drm_vblank.c:1329, CPU#2: kworker/2:4/5833
Modules linked in:
CPU: 2 UID: 0 PID: 5833 Comm: kworker/2:4 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events drm_fb_helper_damage_work
RIP: 0010:drm_crtc_wait_one_vblank+0x323/0x580 drivers/gpu/drm/drm_vblank.c:1329
Code: 48 8b 6b 50 48 85 ed 0f 84 dc 01 00 00 e8 05 42 32 fc 48 89 df e8 2d 38 92 00 48 89 c6 48 8d 3d e3 29 78 0c 44 89 e9 48 89 ea <67> 48 0f b9 3a 44 89 ee 4c 89 e7 41 be 92 ff ff ff e8 57 f7 ff ff
RSP: 0018:ffffc90004c7fa40 EFLAGS: 00010293
RAX: ffffffff8c92c680 RBX: ffff8880229e20d0 RCX: 0000000000000000
RDX: ffff888022344e80 RSI: ffffffff8c92c680 RDI: ffffffff9251a400
RBP: ffff888022344e80 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff81d6ced9 R12: ffff888041b74000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000007e3a
FS:  0000000000000000(0000) GS:ffff888095936000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000f5182a6f CR3: 000000002387b000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000000e DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 drm_client_modeset_wait_for_vblank+0xef/0x120 drivers/gpu/drm/drm_client_modeset.c:1331
 drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:327 [inline]
 drm_fb_helper_damage_work+0x2e2/0xab0 drivers/gpu/drm/drm_fb_helper.c:365
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	48 8b 6b 50          	mov    0x50(%rbx),%rbp
   4:	48 85 ed             	test   %rbp,%rbp
   7:	0f 84 dc 01 00 00    	je     0x1e9
   d:	e8 05 42 32 fc       	call   0xfc324217
  12:	48 89 df             	mov    %rbx,%rdi
  15:	e8 2d 38 92 00       	call   0x923847
  1a:	48 89 c6             	mov    %rax,%rsi
  1d:	48 8d 3d e3 29 78 0c 	lea    0xc7829e3(%rip),%rdi        # 0xc782a07
  24:	44 89 e9             	mov    %r13d,%ecx
  27:	48 89 ea             	mov    %rbp,%rdx
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	44 89 ee             	mov    %r13d,%esi
  32:	4c 89 e7             	mov    %r12,%rdi
  35:	41 be 92 ff ff ff    	mov    $0xffffff92,%r14d
  3b:	e8 57 f7 ff ff       	call   0xfffff797