On Fri, 2022-05-20 at 00:35 +0200, 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.

Thanks.

Reviewed-by: Vinod Govindapillai vinod.govindapillai@intel.com

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@intel.com

Hi all,

This is resend of [1]. For unknown reason CC-ing ppl did not work, so I've decided to resend. I hope this time it will work. The patch was already succesfully tested by CI (rev6, rev7 of [1]).

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);