[Intel-gfx] [PATCH v6] drm/i915/display: disable HPD workers before display driver unregister

[Andrzej Hajda]

Seems the patch correctly fixes the the issue and passes CI so added 
maintainers/reviewers to CC.


On 13.05.2022 18:06, Andrzej Hajda wrote:
> Handling HPD during driver removal is pointless, and can cause different
> use-after-free/concurrency issues:
> 1. Setup of deferred fbdev after fbdev unregistration.
> 2. Access to DP-AUX after DP-AUX removal.
> 
> Below stacktraces of both cases observed on CI:
> 
> [272.634530] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP NOPTI
> [272.634536] CPU: 0 PID: 6030 Comm: i915_selftest Tainted: G     U            5.18.0-rc5-CI_DRM_11603-g12dccf4f5eef+ #1
> [272.634541] Hardware name: Intel Corporation Raptor Lake Client Platform/RPL-S ADP-S DDR5 UDIMM CRB, BIOS RPLSFWI1.R00.2397.A01.2109300731 09/30/2021
> [272.634545] RIP: 0010:fb_do_apertures_overlap.part.14+0x26/0x60
> ...
> [272.634582] Call Trace:
> [272.634583]  <TASK>
> [272.634585]  do_remove_conflicting_framebuffers+0x59/0xa0
> [272.634589]  remove_conflicting_framebuffers+0x2d/0xc0
> [272.634592]  remove_conflicting_pci_framebuffers+0xc8/0x110
> [272.634595]  drm_aperture_remove_conflicting_pci_framebuffers+0x52/0x70
> [272.634604]  i915_driver_probe+0x63a/0xdd0 [i915]
> 
> [283.405824] cpu_latency_qos_update_request called for unknown object
> [283.405866] WARNING: CPU: 2 PID: 240 at kernel/power/qos.c:296 cpu_latency_qos_update_request+0x2d/0x100
> [283.405912] CPU: 2 PID: 240 Comm: kworker/u64:9 Not tainted 5.18.0-rc6-Patchwork_103738v3-g1672d1c43e43+ #1
> [283.405915] Hardware name: Intel Corporation Raptor Lake Client Platform/RPL-S ADP-S DDR5 UDIMM CRB, BIOS RPLSFWI1.R00.2397.A01.2109300731 09/30/2021
> [283.405916] Workqueue: i915-dp i915_digport_work_func [i915]
> [283.406020] RIP: 0010:cpu_latency_qos_update_request+0x2d/0x100
> ...
> [283.406040] Call Trace:
> [283.406041]  <TASK>
> [283.406044]  intel_dp_aux_xfer+0x60e/0x8e0 [i915]
> [283.406131]  ? finish_swait+0x80/0x80
> [283.406139]  intel_dp_aux_transfer+0xc5/0x2b0 [i915]
> [283.406218]  drm_dp_dpcd_access+0x79/0x130 [drm_display_helper]
> [283.406227]  drm_dp_dpcd_read+0xe2/0xf0 [drm_display_helper]
> [283.406233]  intel_dp_hpd_pulse+0x134/0x570 [i915]
> [283.406308]  ? __down_killable+0x70/0x140
> [283.406313]  i915_digport_work_func+0xba/0x150 [i915]
> 
> Signed-off-by: Andrzej Hajda <andrzej.hajda at intel.com>
> ---
> Hi all,
> 
> This is my Nth attempt to solve some old CI bug[1].
> v-2: caused issues in kms code [2],
> v-1: revealed that not only fbdev does not like HPD on removal [3],
> v3: lacks drm_kms_helper_poll_disable[4]
> v4: added dump_stack to detect late fb registration
> v5: added intel_dp_mst_suspend to stop late fb registration
> v6: removed dump_stack with hope everything is handled
> 
> Moreover this is quite rare bug, but due to specific configuration
> of one of CI machines it appears there very frequently.
> Forgive me spamming the list.
> 
> [1]: https://gitlab.freedesktop.org/drm/intel/-/issues/5329
> [2]: https://patchwork.freedesktop.org/series/103621/
> [3]: https://patchwork.freedesktop.org/series/103738/
> [4]: https://patchwork.freedesktop.org/series/103811/
> 
> Regards
> Andrzej
> ---
>   drivers/gpu/drm/i915/display/intel_display.c | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 806d50b302ab92..007bc6daef7d31 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -10486,13 +10486,6 @@ void intel_modeset_driver_remove_noirq(struct drm_i915_private *i915)
>   	 */
>   	intel_hpd_poll_fini(i915);
>   
> -	/*
> -	 * MST topology needs to be suspended so we don't have any calls to
> -	 * fbdev after it's finalized. MST will be destroyed later as part of
> -	 * drm_mode_config_cleanup()
> -	 */
> -	intel_dp_mst_suspend(i915);
> -
>   	/* poll work can call into fbdev, hence clean that up afterwards */
>   	intel_fbdev_fini(i915);
>   
> @@ -10584,6 +10577,10 @@ void intel_display_driver_unregister(struct drm_i915_private *i915)
>   	if (!HAS_DISPLAY(i915))
>   		return;
>   
> +	intel_dp_mst_suspend(i915);
> +	intel_hpd_cancel_work(i915);
> +	drm_kms_helper_poll_disable(&i915->drm);
> +
>   	intel_fbdev_unregister(i915);
>   	intel_audio_deinit(i915);
>