[Intel-gfx] [PATCH v7] drm/i915/display: disable HPD workers before display driver unregister

[Andrzej Hajda]

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,

I am not sure about changes in shutdown path, any comments welcome.
I suspect suspend path have also some common bits, but I am little
bit afraid of touching it.

Changes:
v1 - v6:
    - chasing the bug appearing only on public CI.
v7:
    - shutdown path adjusted (suggested by Jani)

Regards
Andrzej
---
 drivers/gpu/drm/i915/display/intel_display.c | 11 ++++-------
 drivers/gpu/drm/i915/i915_driver.c           |  5 ++---
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 186b37925d23f2..f9952ee8289fb2 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -10490,13 +10490,6 @@ 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);
 
@@ -10588,6 +10581,10 @@ 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);
 
diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
index d26dcca7e654aa..82cdccf072e2bc 100644
--- a/drivers/gpu/drm/i915/i915_driver.c
+++ b/drivers/gpu/drm/i915/i915_driver.c
@@ -1070,15 +1070,14 @@ void i915_driver_shutdown(struct drm_i915_private *i915)
 	i915_gem_suspend(i915);
 
 	if (HAS_DISPLAY(i915)) {
+		intel_dp_mst_suspend(i915);
+		intel_hpd_cancel_work(i915);
 		drm_kms_helper_poll_disable(&i915->drm);
 
 		drm_atomic_helper_shutdown(&i915->drm);
 	}
 
-	intel_dp_mst_suspend(i915);
-
 	intel_runtime_pm_disable_interrupts(i915);
-	intel_hpd_cancel_work(i915);
 
 	intel_suspend_encoders(i915);
 	intel_shutdown_encoders(i915);
-- 
2.25.1