Re: Bug#1054514: linux-image-6.1.0-13-amd64: Debian VM with qxl graphics freezes frequently

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + moreinfo

Hi Matt,

On Tue, Dec 09, 2025 at 10:33:24AM -0800, Matt Marjanovic wrote:
> Package: src:linux
> Version: 6.12.57-1
> Followup-For: Bug #1054514
> 
> Dear Maintainer,
> 
> This is back in trixie --- unsurprisingly, because the kernel commit which
> had originally caused this bug, and was subsequently reverted, was reapplied
> to the kernel in 6.8.10:
> 
>   https://www.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.8.10
>   (Reapply "drm/qxl: simplify qxl_fence_wait")
> 
> In addition to making the remote graphics freeze (which is annoying but
> tolerable), the graphics driver hang also appears to cause systemd tasks
> to hang... which leads to problems with remote login via ssh, and also
> the inability to do a clean reboot/shutdown (which is intolerable).
> 
> Sample of the kernel log for hung systemd task (bookended by the telltale
> "Buffer eviction failed" every 15 seconds):
> 
> [413120.319715] INFO: task systemd:1 blocked for more than 1208 seconds.
> [413120.319718]       Not tainted 6.12.57+deb13-amd64 #1 Debian 6.12.57-1
> [413120.319719] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [413120.319720] task:systemd         state:D stack:0     pid:1     tgid:1     ppid:0      flags:0x00000002
> [413120.319723] Call Trace:
> [413120.319724]  <TASK>
> [413120.319726]  __schedule+0x505/0xc00
> [413120.319730]  schedule+0x27/0xf0
> [413120.319732]  schedule_preempt_disabled+0x15/0x30
> [413120.319733]  __ww_mutex_lock.constprop.0+0x4f6/0x9a0
> [413120.319736]  drm_modeset_lock+0x42/0xe0 [drm]
> [413120.319765]  drm_atomic_get_plane_state+0x7f/0x180 [drm]
> [413120.319777]  drm_client_modeset_commit_atomic+0xbf/0x250 [drm]
> [413120.319793]  ? do_sys_poll+0x4e1/0x600
> [413120.319796]  drm_client_modeset_commit_locked+0x5a/0x160 [drm]
> [413120.319810]  drm_fb_helper_pan_display+0xf2/0x240 [drm_kms_helper]
> [413120.319819]  fb_pan_display+0x89/0x140
> [413120.319821]  bit_update_start+0x1e/0x40
> [413120.319822]  fbcon_switch+0x421/0x5b0
> [413120.319825]  csi_J+0x286/0x2d0
> [413120.319826]  do_con_write+0x1368/0x2440
> [413120.319828]  ? tomoyo_path_number_perm+0x8c/0x1f0
> [413120.319830]  ? _prb_read_valid+0x298/0x310
> [413120.319832]  con_write+0x13/0x50
> [413120.319833]  n_tty_write+0x15a/0x500
> [413120.319835]  ? __pfx_woken_wake_function+0x10/0x10
> [413120.319837]  file_tty_write.isra.0+0x172/0x2c0
> [413120.319840]  vfs_write+0x28c/0x440
> [413120.319842]  ksys_write+0x6d/0xf0
> [413120.319844]  do_syscall_64+0x82/0x190
> [413120.319845]  ? tty_ioctl+0x145/0x8a0
> [413120.319847]  ? arch_exit_to_user_mode_prepare.isra.0+0x16/0xa0
> [413120.319850]  ? syscall_exit_to_user_mode+0x37/0x1b0
> [413120.319851]  ? do_syscall_64+0x8e/0x190
> [413120.319852]  ? do_sys_openat2+0x9c/0xe0
> [413120.319853]  ? do_syscall_64+0x8e/0x190
> [413120.319854]  ? arch_exit_to_user_mode_prepare.isra.0+0x16/0xa0
> [413120.319856]  ? syscall_exit_to_user_mode+0x37/0x1b0
> [413120.319857]  ? do_syscall_64+0x8e/0x190
> [413120.319858]  ? __x64_sys_ppoll+0xf4/0x160
> [413120.319859]  ? arch_exit_to_user_mode_prepare.isra.0+0x16/0xa0
> [413120.319861]  ? syscall_exit_to_user_mode+0x37/0x1b0
> [413120.319862]  ? do_syscall_64+0x8e/0x190
> [413120.319862]  ? clear_bhb_loop+0x40/0x90
> [413120.319864]  ? clear_bhb_loop+0x40/0x90
> [413120.319865]  ? clear_bhb_loop+0x40/0x90
> [413120.319866]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [413120.319869] RIP: 0033:0x7f38ba499687
> [413120.319878] RSP: 002b:00007ffd7e321560 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
> [413120.319879] RAX: ffffffffffffffda RBX: 00007f38baa3ee00 RCX: 00007f38ba499687
> [413120.319880] RDX: 000000000000000c RSI: 00007f38ba927cc4 RDI: 0000000000000025
> [413120.319881] RBP: 0000000000000025 R08: 0000000000000000 R09: 0000000000000000
> [413120.319881] R10: 0000000000000000 R11: 0000000000000202 R12: 00000000000186a0
> [413120.319882] R13: 0000005fe7e4b3fb R14: 000000000000000c R15: 0000000000000025
> [413120.319883]  </TASK>
> [413120.319884] Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings
> [413123.903768] [TTM] Buffer eviction failed
> [413139.007582] [TTM] Buffer eviction failed
> [413154.111473] [TTM] Buffer eviction failed
> [413169.215198] [TTM] Buffer eviction failed
> [413184.319084] [TTM] Buffer eviction failed
> [413199.422894] [TTM] Buffer eviction failed
> [413214.526697] [TTM] Buffer eviction failed

I guess it is very unlikely that the commit get reverted again, given
the reasons explained in the commit message on the re-apply.

But can you please confirm that reverting the commit on top of 6.12.y
fixes the issue again for you?

Note that it has even be re-applied to 6.1.y, actually form 6.9 back
to 6.8.10, 6.6.31, 6.1.91 and 5.15.159.

Is the issue still as well triggerable in 6.17.11 and mainline?

Regards,
Salvatore