Re: [PATCH 07/12] drm/i915: Prevent modesets during driver init/shutdown

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Thu, 2024-01-04 at 10:30 +0200, Imre Deak wrote:
> An unexpected modeset or connector detection by a user (user space or
> FB
> console) during the initialization/shutdown sequence is possible
> either
> via a hotplug IRQ handling work or via the connector sysfs
> (status/detect) interface. These modesets/detections should be
> prevented
> by disabling/flushing all related hotplug handling work and
> unregistering the interfaces that can start them at the beginning of
> the
> shutdown sequence. Some of this - disabling all related intel_hotplug
> work - will be done by the next patch, but others - for instance
> disabling the MST hotplug works - require a bigger rework.
> 
> It makes sense - for diagnostic purpose, even with all the above work
> and
> interface disabled - to detect and reject any such user access. This
> patch does that for modeset accesses and a follow-up patch for
> connector
> detection.
> 
> After the display is disabled during the shutdown sequence, no
> modeset
> should happen so it's disabled for both users and the shutdown
> thread.

Can you please explain in commit message why
intel_display_driver_disable_user_access and
intel_display_driver_resume_access are allowing modeset for "current"
process?

BR,

Jouni Högander

> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c  |  3 +
>  .../gpu/drm/i915/display/intel_display_core.h |  7 ++
>  .../drm/i915/display/intel_display_driver.c   | 74
> +++++++++++++++++++
>  .../drm/i915/display/intel_display_driver.h   |  6 ++
>  drivers/gpu/drm/i915/i915_driver.c            | 16 +++-
>  5 files changed, 104 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index 927d124457b61..31a6a82c12616 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -6310,6 +6310,9 @@ int intel_atomic_check(struct drm_device *dev,
>         int ret, i;
>         bool any_ms = false;
>  
> +       if (!intel_display_driver_check_access(dev_priv))
> +               return -ENODEV;
> +
>         for_each_oldnew_intel_crtc_in_state(state, crtc,
> old_crtc_state,
>                                             new_crtc_state, i) {
>                 /*
> diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h
> b/drivers/gpu/drm/i915/display/intel_display_core.h
> index 47297ed858223..0b130ca9e6698 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_core.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_core.h
> @@ -28,6 +28,8 @@
>  #include "intel_opregion.h"
>  #include "intel_wm_types.h"
>  
> +struct task_struct;
> +
>  struct drm_i915_private;
>  struct drm_property;
>  struct drm_property_blob;
> @@ -298,6 +300,11 @@ struct intel_display {
>                 const struct intel_audio_funcs *audio;
>         } funcs;
>  
> +       struct {
> +               bool any_task_allowed;
> +               struct task_struct *allowed_task;
> +       } access;
> +
>         struct {
>                 /* backlight registers and fields in struct
> intel_panel */
>                 struct mutex lock;
> diff --git a/drivers/gpu/drm/i915/display/intel_display_driver.c
> b/drivers/gpu/drm/i915/display/intel_display_driver.c
> index 1974f2394a518..b2441ab9822c2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_driver.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_driver.c
> @@ -45,6 +45,7 @@
>  #include "intel_hdcp.h"
>  #include "intel_hotplug.h"
>  #include "intel_hti.h"
> +#include "intel_modeset_lock.h"
>  #include "intel_modeset_setup.h"
>  #include "intel_opregion.h"
>  #include "intel_overlay.h"
> @@ -276,6 +277,71 @@ int intel_display_driver_probe_noirq(struct
> drm_i915_private *i915)
>         return ret;
>  }
>  
> +static void set_display_access(struct drm_i915_private *i915,
> +                              bool any_task_allowed,
> +                              struct task_struct *allowed_task)
> +{
> +       struct drm_modeset_acquire_ctx ctx;
> +       int err;
> +
> +       intel_modeset_lock_ctx_retry(&ctx, NULL, 0, err) {
> +               err = drm_modeset_lock_all_ctx(&i915->drm, &ctx);
> +               if (err)
> +                       continue;
> +
> +               i915->display.access.any_task_allowed =
> any_task_allowed;
> +               i915->display.access.allowed_task = allowed_task;
> +       }
> +
> +       drm_WARN_ON(&i915->drm, err);
> +}
> +
> +void intel_display_driver_enable_user_access(struct drm_i915_private
> *i915)
> +{
> +       set_display_access(i915, true, NULL);
> +}
> +
> +void intel_display_driver_disable_user_access(struct
> drm_i915_private *i915)
> +{
> +       set_display_access(i915, false, current);
> +}
> +
> +void intel_display_driver_suspend_access(struct drm_i915_private
> *i915)
> +{
> +       set_display_access(i915, false, NULL);
> +}
> +
> +void intel_display_driver_resume_access(struct drm_i915_private
> *i915)
> +{
> +       set_display_access(i915, false, current);
> +}
> +
> +bool intel_display_driver_check_access(struct drm_i915_private
> *i915)
> +{
> +       char comm[TASK_COMM_LEN];
> +       char current_task[TASK_COMM_LEN + 16];
> +       char allowed_task[TASK_COMM_LEN + 16] = "none";
> +
> +       if (i915->display.access.any_task_allowed ||
> +           i915->display.access.allowed_task == current)
> +               return true;
> +
> +       snprintf(current_task, sizeof(current_task), "%s[%d]",
> +                get_task_comm(comm, current),
> +                task_pid_vnr(current));
> +
> +       if (i915->display.access.allowed_task)
> +               snprintf(allowed_task, sizeof(allowed_task),
> "%s[%d]",
> +                        get_task_comm(comm, i915-
> >display.access.allowed_task),
> +                        task_pid_vnr(i915-
> >display.access.allowed_task));
> +
> +       drm_dbg_kms(&i915->drm,
> +                   "Reject display access from task %s (allowed to
> %s)\n",
> +                   current_task, allowed_task);
> +
> +       return false;
> +}
> +
>  /* part #2: call after irq install, but before gem init */
>  int intel_display_driver_probe_nogem(struct drm_i915_private *i915)
>  {
> @@ -326,6 +392,8 @@ int intel_display_driver_probe_nogem(struct
> drm_i915_private *i915)
>         intel_vga_disable(i915);
>         intel_setup_outputs(i915);
>  
> +       intel_display_driver_disable_user_access(i915);
> +
>         drm_modeset_lock_all(dev);
>         intel_modeset_setup_hw_state(i915, dev-
> >mode_config.acquire_ctx);
>         intel_acpi_assign_connector_fwnodes(i915);
> @@ -393,6 +461,8 @@ void intel_display_driver_register(struct
> drm_i915_private *i915)
>  
>         intel_audio_init(i915);
>  
> +       intel_display_driver_enable_user_access(i915);
> +
>         intel_display_debugfs_register(i915);
>  
>         /*
> @@ -440,6 +510,8 @@ void intel_display_driver_remove_noirq(struct
> drm_i915_private *i915)
>         if (!HAS_DISPLAY(i915))
>                 return;
>  
> +       intel_display_driver_suspend_access(i915);
> +
>         /*
>          * Due to the hpd irq storm handling the hotplug work can re-
> arm the
>          * poll handlers. Hence disable polling after hpd handling is
> shut down.
> @@ -493,6 +565,8 @@ void intel_display_driver_unregister(struct
> drm_i915_private *i915)
>          */
>         drm_kms_helper_poll_fini(&i915->drm);
>  
> +       intel_display_driver_disable_user_access(i915);
> +
>         intel_audio_deinit(i915);
>  
>         drm_atomic_helper_shutdown(&i915->drm);
> diff --git a/drivers/gpu/drm/i915/display/intel_display_driver.h
> b/drivers/gpu/drm/i915/display/intel_display_driver.h
> index c276a58ee3293..42cc4af6d3fd5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_driver.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_driver.h
> @@ -32,5 +32,11 @@ int __intel_display_driver_resume(struct
> drm_i915_private *i915,
>                                   struct drm_atomic_state *state,
>                                   struct drm_modeset_acquire_ctx
> *ctx);
>  
> +void intel_display_driver_enable_user_access(struct drm_i915_private
> *i915);
> +void intel_display_driver_disable_user_access(struct
> drm_i915_private *i915);
> +void intel_display_driver_suspend_access(struct drm_i915_private
> *i915);
> +void intel_display_driver_resume_access(struct drm_i915_private
> *i915);
> +bool intel_display_driver_check_access(struct drm_i915_private
> *i915);
> +
>  #endif /* __INTEL_DISPLAY_DRIVER_H__ */
>  
> diff --git a/drivers/gpu/drm/i915/i915_driver.c
> b/drivers/gpu/drm/i915/i915_driver.c
> index 166476948c896..068ca48e05323 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -1006,6 +1006,7 @@ void i915_driver_shutdown(struct
> drm_i915_private *i915)
>         intel_fbdev_set_suspend(&i915->drm, FBINFO_STATE_SUSPENDED,
> true);
>         if (HAS_DISPLAY(i915)) {
>                 drm_kms_helper_poll_disable(&i915->drm);
> +               intel_display_driver_disable_user_access(i915);
>  
>                 drm_atomic_helper_shutdown(&i915->drm);
>         }
> @@ -1015,6 +1016,8 @@ void i915_driver_shutdown(struct
> drm_i915_private *i915)
>         intel_runtime_pm_disable_interrupts(i915);
>         intel_hpd_cancel_work(i915);
>  
> +       intel_display_driver_suspend_access(i915);
> +
>         intel_suspend_encoders(i915);
>         intel_shutdown_encoders(i915);
>  
> @@ -1082,8 +1085,10 @@ static int i915_drm_suspend(struct drm_device
> *dev)
>          * properly. */
>         intel_power_domains_disable(dev_priv);
>         intel_fbdev_set_suspend(dev, FBINFO_STATE_SUSPENDED, true);
> -       if (HAS_DISPLAY(dev_priv))
> +       if (HAS_DISPLAY(dev_priv)) {
>                 drm_kms_helper_poll_disable(dev);
> +               intel_display_driver_disable_user_access(dev_priv);
> +       }
>  
>         pci_save_state(pdev);
>  
> @@ -1094,6 +1099,8 @@ static int i915_drm_suspend(struct drm_device
> *dev)
>         intel_runtime_pm_disable_interrupts(dev_priv);
>         intel_hpd_cancel_work(dev_priv);
>  
> +       intel_display_driver_suspend_access(dev_priv);
> +
>         intel_suspend_encoders(dev_priv);
>  
>         /* Must be called before GGTT is suspended. */
> @@ -1243,14 +1250,19 @@ static int i915_drm_resume(struct drm_device
> *dev)
>         intel_display_driver_init_hw(dev_priv);
>  
>         intel_clock_gating_init(dev_priv);
> +
> +       intel_display_driver_resume_access(dev_priv);
> +
>         intel_hpd_init(dev_priv);
>  
>         /* MST sideband requires HPD interrupts enabled */
>         intel_dp_mst_resume(dev_priv);
>         intel_display_driver_resume(dev_priv);
>  
> -       if (HAS_DISPLAY(dev_priv))
> +       if (HAS_DISPLAY(dev_priv)) {
> +               intel_display_driver_enable_user_access(dev_priv);
>                 drm_kms_helper_poll_enable(dev);
> +       }
>         intel_hpd_poll_disable(dev_priv);
>  
>         intel_opregion_resume(dev_priv);