Re: [Intel-gfx] [PATCH v12 1/1] drm/i915/pxp: Promote pxp subsystem to top-level of i915
On 12/8/2022 10:05 AM, Alan Previn wrote: Starting with MTL, there will be two GT-tiles, a render and media tile. PXP as a service for supporting workloads with protected contexts and protected buffers can be subscribed by process workloads on any tile. However, depending on the platform, only one of the tiles is used for control events pertaining to PXP operation (such as creating the arbitration session and session tear-down). PXP as a global feature is accessible via batch buffer instructions on any engine/tile and the coherency across tiles is handled implicitly by the HW. In fact, for the foreseeable future, we are expecting this single-control-tile for the PXP subsystem. In MTL, it's the standalone media tile (not the root tile) because it contains the VDBOX and KCR engine (among the assets PXP relies on for those events). Looking at the current code design, each tile is represented by the intel_gt structure while the intel_pxp structure currently hangs off the intel_gt structure. Keeping the intel_pxp structure within the intel_gt structure makes some internal functionalities more straight forward but adds code complexity to code readability and maintainibility to many external-to-pxp subsystems which may need to pick the correct intel_gt structure. An example of this would be the intel_pxp_is_active or intel_pxp_is_enabled functionality which should be viewed as a global level inquiry, not a per-gt inquiry. That said, this series promotes the intel_pxp structure into the drm_i915_private structure making it a top-level subsystem and the PXP subsystem will select the control gt internally and keep a pointer to it for internal reference. This promotion comes with two noteworthy changes: 1. Exported pxp functions that are called by external subsystems (such as intel_pxp_enabled/active) will have to check implicitly if i915->pxp is valid as that structure will not be allocated for HW that doesn't support PXP. 2. Since GT is now considered a soft-dependency of PXP we are ensuring that GT init happens before PXP init and vice versa for fini. This causes a minor ordering change whereby we previously called intel_pxp_suspend after intel_uc_suspend but now is before i915_gem_suspend_late but the change is required for correct dependency flows. Additionally, this re-order change doesn't have any impact because at that point in either case, the top level entry to i915 won't observe any PXP events (since the GPU was quiesced during suspend_prepare). Also, any PXP event doesn't really matter when we disable the PXP HW (global GT irqs are already off anyway, so even if there was a bug that generated spurious events we wouldn't see it and we would just clean it up on resume which is okay since the default fallback action for PXP would be to keep the sessions off at this suspend stage). Changes from prior revs: v11: - Reformat a comment (Tvrtko). v10: - Change the code flow for intel_pxp_init to make it more cleaner and readible with better comments explaining the difference between full-PXP-feature vs the partial-teelink inits depending on the platform. Additionally, only do the pxp allocation when we are certain the subsystem is needed. (Tvrtko). v9: - Cosmetic cleanups in supported/enabled/active. (Daniele). - Add comments for intel_pxp_init and pxp_get_ctrl_gt that explain the functional flow for when PXP is not supported but the backend-assets are needed for HuC authentication (Daniele and Tvrtko). - Fix two remaining functions that are accessible outside PXP that need to be checking pxp ptrs before using them: intel_pxp_irq_handler and intel_pxp_huc_load_and_auth (Tvrtko and Daniele). - User helper macro in pxp-debugfs (Tvrtko). v8: - Remove pxp_to_gt macro (Daniele). - Fix a bug in pxp_get_ctrl_gt for the case of MTL and we don't support GSC-FW on it. (Daniele). - Leave i915->pxp as NULL if we dont support PXP and in line with that, do additional validity check on i915->pxp for intel_pxp_is_supported/enabled/active (Daniele). - Remove unncessary include header from intel_gt_debugfs.c and check drm_minor i915->drm.primary (Daniele). - Other cosmetics / minor issues / more comments on suspend flow order change (Daniele). v7: - Drop i915_dev_to_pxp and in intel_pxp_init use 'i915->pxp' through out instead of local variable newpxp. (Rodrigo) - In the case intel_pxp_fini is called during driver unload but after i915 loading failed without pxp being allocated, check i915->pxp before referencing it. (Alan) v6: - Remove HAS_PXP macro and replace it with intel_pxp_is_supported because : [1] introduction of 'ctrl_gt' means we correct this for MTL's
[Intel-gfx] [PATCH v12 1/1] drm/i915/pxp: Promote pxp subsystem to top-level of i915
Starting with MTL, there will be two GT-tiles, a render and media tile. PXP as a service for supporting workloads with protected contexts and protected buffers can be subscribed by process workloads on any tile. However, depending on the platform, only one of the tiles is used for control events pertaining to PXP operation (such as creating the arbitration session and session tear-down). PXP as a global feature is accessible via batch buffer instructions on any engine/tile and the coherency across tiles is handled implicitly by the HW. In fact, for the foreseeable future, we are expecting this single-control-tile for the PXP subsystem. In MTL, it's the standalone media tile (not the root tile) because it contains the VDBOX and KCR engine (among the assets PXP relies on for those events). Looking at the current code design, each tile is represented by the intel_gt structure while the intel_pxp structure currently hangs off the intel_gt structure. Keeping the intel_pxp structure within the intel_gt structure makes some internal functionalities more straight forward but adds code complexity to code readability and maintainibility to many external-to-pxp subsystems which may need to pick the correct intel_gt structure. An example of this would be the intel_pxp_is_active or intel_pxp_is_enabled functionality which should be viewed as a global level inquiry, not a per-gt inquiry. That said, this series promotes the intel_pxp structure into the drm_i915_private structure making it a top-level subsystem and the PXP subsystem will select the control gt internally and keep a pointer to it for internal reference. This promotion comes with two noteworthy changes: 1. Exported pxp functions that are called by external subsystems (such as intel_pxp_enabled/active) will have to check implicitly if i915->pxp is valid as that structure will not be allocated for HW that doesn't support PXP. 2. Since GT is now considered a soft-dependency of PXP we are ensuring that GT init happens before PXP init and vice versa for fini. This causes a minor ordering change whereby we previously called intel_pxp_suspend after intel_uc_suspend but now is before i915_gem_suspend_late but the change is required for correct dependency flows. Additionally, this re-order change doesn't have any impact because at that point in either case, the top level entry to i915 won't observe any PXP events (since the GPU was quiesced during suspend_prepare). Also, any PXP event doesn't really matter when we disable the PXP HW (global GT irqs are already off anyway, so even if there was a bug that generated spurious events we wouldn't see it and we would just clean it up on resume which is okay since the default fallback action for PXP would be to keep the sessions off at this suspend stage). Changes from prior revs: v11: - Reformat a comment (Tvrtko). v10: - Change the code flow for intel_pxp_init to make it more cleaner and readible with better comments explaining the difference between full-PXP-feature vs the partial-teelink inits depending on the platform. Additionally, only do the pxp allocation when we are certain the subsystem is needed. (Tvrtko). v9: - Cosmetic cleanups in supported/enabled/active. (Daniele). - Add comments for intel_pxp_init and pxp_get_ctrl_gt that explain the functional flow for when PXP is not supported but the backend-assets are needed for HuC authentication (Daniele and Tvrtko). - Fix two remaining functions that are accessible outside PXP that need to be checking pxp ptrs before using them: intel_pxp_irq_handler and intel_pxp_huc_load_and_auth (Tvrtko and Daniele). - User helper macro in pxp-debugfs (Tvrtko). v8: - Remove pxp_to_gt macro (Daniele). - Fix a bug in pxp_get_ctrl_gt for the case of MTL and we don't support GSC-FW on it. (Daniele). - Leave i915->pxp as NULL if we dont support PXP and in line with that, do additional validity check on i915->pxp for intel_pxp_is_supported/enabled/active (Daniele). - Remove unncessary include header from intel_gt_debugfs.c and check drm_minor i915->drm.primary (Daniele). - Other cosmetics / minor issues / more comments on suspend flow order change (Daniele). v7: - Drop i915_dev_to_pxp and in intel_pxp_init use 'i915->pxp' through out instead of local variable newpxp. (Rodrigo) - In the case intel_pxp_fini is called during driver unload but after i915 loading failed without pxp being allocated, check i915->pxp before referencing it. (Alan) v6: - Remove HAS_PXP macro and replace it with intel_pxp_is_supported because : [1] introduction of 'ctrl_gt' means we correct this for MTL's upcoming series now. [2] Also, this has little impact globally as its only used by
