Re: [syzbot] [dri?] WARNING in drm_atomic_helper_wait_for_vblanks (6)

syzbot has found a reproducer for the following issue on:

HEAD commit:    b643e495ae92 Merge tag 's390-7.2-7' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=176c0079580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=45bc7264de77caad91cb
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15cbc079580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=138fa2c6580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-b643e495.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9eb4fbda136d/vmlinux-b643e495.xz
kernel image: https://storage.googleapis.com/syzbot-assets/53cbbd75c40a/bzImage-b643e495.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

------------[ cut here ]------------
[CRTC:39:crtc-0] vblank wait timed out
WARNING: drivers/gpu/drm/drm_atomic_helper.c:1921 at drm_atomic_helper_wait_for_vblanks.part.0+0x738/0x8a0 drivers/gpu/drm/drm_atomic_helper.c:1921, CPU#3: syz.0.17/5906
Modules linked in:
CPU: 3 UID: 0 PID: 5906 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:drm_atomic_helper_wait_for_vblanks.part.0+0x73e/0x8a0 drivers/gpu/drm/drm_atomic_helper.c:1921
Code: 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 0f b6 04 01 84 c0 74 08 3c 03 0f 8e 44 01 00 00 48 8d 3d 48 de 5f 0b 8b b3 d0 00 00 00 <67> 48 0f b9 3a e9 e1 fc ff ff e8 93 10 3d fc e9 7c fe ff ff e8 99
RSP: 0018:ffffc90003847710 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888028680040 RCX: 1ffff110050d0022
RDX: ffff8880285a50e0 RSI: 0000000000000027 RDI: ffffffff912d4120
RBP: dffffc0000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88802e1f5000
FS:  000055557c115500(0000) GS:ffff8880d60ec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055777c801168 CR3: 000000005176b000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 drm_atomic_helper_wait_for_vblanks drivers/gpu/drm/drm_atomic_helper.c:1895 [inline]
 drm_atomic_helper_commit_tail+0xff/0x130 drivers/gpu/drm/drm_atomic_helper.c:1997
 commit_tail+0x338/0x430 drivers/gpu/drm/drm_atomic_helper.c:2074
 drm_atomic_helper_commit+0x303/0x380 drivers/gpu/drm/drm_atomic_helper.c:2312
 drm_atomic_commit+0x230/0x300 drivers/gpu/drm/drm_atomic.c:1789
 drm_atomic_helper_set_config+0x13a/0x190 drivers/gpu/drm/drm_atomic_helper.c:3523
 drm_mode_setcrtc+0xeca/0x1d50 drivers/gpu/drm/drm_crtc.c:885
 drm_ioctl_kernel+0x1f3/0x3e0 drivers/gpu/drm/drm_ioctl.c:817
 drm_ioctl+0x5e6/0xc60 drivers/gpu/drm/drm_ioctl.c:914
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6d5bf9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe900c07d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6d5c225fa0 RCX: 00007f6d5bf9e0d9
RDX: 0000200000000300 RSI: 00000000c06864a2 RDI: 0000000000000003
RBP: 00007f6d5c035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6d5c225fac R14: 00007f6d5c225fa0 R15: 00007f6d5c225fa0
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	00 fc                	add    %bh,%ah
   4:	ff                   	lcall  (bad)
   5:	df 48 89             	fisttps -0x77(%rax)
   8:	f9                   	stc
   9:	48 c1 e9 03          	shr    $0x3,%rcx
   d:	0f b6 04 01          	movzbl (%rcx,%rax,1),%eax
  11:	84 c0                	test   %al,%al
  13:	74 08                	je     0x1d
  15:	3c 03                	cmp    $0x3,%al
  17:	0f 8e 44 01 00 00    	jle    0x161
  1d:	48 8d 3d 48 de 5f 0b 	lea    0xb5fde48(%rip),%rdi        # 0xb5fde6c
  24:	8b b3 d0 00 00 00    	mov    0xd0(%rbx),%esi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 e1 fc ff ff       	jmp    0xfffffd15
  34:	e8 93 10 3d fc       	call   0xfc3d10cc
  39:	e9 7c fe ff ff       	jmp    0xfffffeba
  3e:	e8                   	.byte 0xe8
  3f:	99                   	cltd


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