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diff --git a/Documentation/gpu/rfc/xe.rst b/Documentation/gpu/rfc/xe.rst deleted file mode 100644 index 97cf87578f..0000000000 --- a/Documentation/gpu/rfc/xe.rst +++ /dev/null @@ -1,234 +0,0 @@ -========================== -Xe – Merge Acceptance Plan -========================== -Xe is a new driver for Intel GPUs that supports both integrated and -discrete platforms starting with Tiger Lake (first Intel Xe Architecture). - -This document aims to establish a merge plan for the Xe, by writing down clear -pre-merge goals, in order to avoid unnecessary delays. - -Xe – Overview -============= -The main motivation of Xe is to have a fresh base to work from that is -unencumbered by older platforms, whilst also taking the opportunity to -rearchitect our driver to increase sharing across the drm subsystem, both -leveraging and allowing us to contribute more towards other shared components -like TTM and drm/scheduler. - -This is also an opportunity to start from the beginning with a clean uAPI that is -extensible by design and already aligned with the modern userspace needs. For -this reason, the memory model is solely based on GPU Virtual Address space -bind/unbind (‘VM_BIND’) of GEM buffer objects (BOs) and execution only supporting -explicit synchronization. With persistent mapping across the execution, the -userspace does not need to provide a list of all required mappings during each -submission. - -The new driver leverages a lot from i915. As for display, the intent is to share -the display code with the i915 driver so that there is maximum reuse there. - -As for the power management area, the goal is to have a much-simplified support -for the system suspend states (S-states), PCI device suspend states (D-states), -GPU/Render suspend states (R-states) and frequency management. It should leverage -as much as possible all the existent PCI-subsystem infrastructure (pm and -runtime_pm) and underlying firmware components such PCODE and GuC for the power -states and frequency decisions. - -Repository: - -https://gitlab.freedesktop.org/drm/xe/kernel (branch drm-xe-next) - -Xe – Platforms -============== -Currently, Xe is already functional and has experimental support for multiple -platforms starting from Tiger Lake, with initial support in userspace implemented -in Mesa (for Iris and Anv, our OpenGL and Vulkan drivers), as well as in NEO -(for OpenCL and Level0). - -During a transition period, platforms will be supported by both Xe and i915. -However, the force_probe mechanism existent in both drivers will allow only one -official and by-default probe at a given time. - -For instance, in order to probe a DG2 which PCI ID is 0x5690 by Xe instead of -i915, the following set of parameters need to be used: - -``` -i915.force_probe=!5690 xe.force_probe=5690 -``` - -In both drivers, the ‘.require_force_probe’ protection forces the user to use the -force_probe parameter while the driver is under development. This protection is -only removed when the support for the platform and the uAPI are stable. Stability -which needs to be demonstrated by CI results. - -In order to avoid user space regressions, i915 will continue to support all the -current platforms that are already out of this protection. Xe support will be -forever experimental and dependent on the usage of force_probe for these -platforms. - -When the time comes for Xe, the protection will be lifted on Xe and kept in i915. - -Xe – Pre-Merge Goals - Work-in-Progress -======================================= - -Display integration with i915 ------------------------------ -In order to share the display code with the i915 driver so that there is maximum -reuse, the i915/display/ code is built twice, once for i915.ko and then for -xe.ko. Currently, the i915/display code in Xe tree is polluted with many 'ifdefs' -depending on the build target. The goal is to refactor both Xe and i915/display -code simultaneously in order to get a clean result before they land upstream, so -that display can already be part of the initial pull request towards drm-next. - -However, display code should not gate the acceptance of Xe in upstream. Xe -patches will be refactored in a way that display code can be removed, if needed, -from the first pull request of Xe towards drm-next. The expectation is that when -both drivers are part of the drm-tip, the introduction of cleaner patches will be -easier and speed up. - -Xe – uAPI high level overview -============================= - -...Warning: To be done in follow up patches after/when/where the main consensus in various items are individually reached. - -Xe – Pre-Merge Goals - Completed -================================ - -Drm_exec --------- -Helper to make dma_resv locking for a big number of buffers is getting removed in -the drm_exec series proposed in https://patchwork.freedesktop.org/patch/524376/ -If that happens, Xe needs to change and incorporate the changes in the driver. -The goal is to engage with the Community to understand if the best approach is to -move that to the drivers that are using it or if we should keep the helpers in -place waiting for Xe to get merged. - -This item ties into the GPUVA, VM_BIND, and even long-running compute support. - -As a key measurable result, we need to have a community consensus documented in -this document and the Xe driver prepared for the changes, if necessary. - -Userptr integration and vm_bind -------------------------------- -Different drivers implement different ways of dealing with execution of userptr. -With multiple drivers currently introducing support to VM_BIND, the goal is to -aim for a DRM consensus on what’s the best way to have that support. To some -extent this is already getting addressed itself with the GPUVA where likely the -userptr will be a GPUVA with a NULL GEM call VM bind directly on the userptr. -However, there are more aspects around the rules for that and the usage of -mmu_notifiers, locking and other aspects. - -This task here has the goal of introducing a documentation of the basic rules. - -The documentation *needs* to first live in this document (API session below) and -then moved to another more specific document or at Xe level or at DRM level. - -Documentation should include: - - * The userptr part of the VM_BIND api. - - * Locking, including the page-faulting case. - - * O(1) complexity under VM_BIND. - -The document is now included in the drm documentation :doc:`here </gpu/drm-vm-bind-async>`. - -Some parts of userptr like mmu_notifiers should become GPUVA or DRM helpers when -the second driver supporting VM_BIND+userptr appears. Details to be defined when -the time comes. - -The DRM GPUVM helpers do not yet include the userptr parts, but discussions -about implementing them are ongoing. - -ASYNC VM_BIND -------------- -Although having a common DRM level IOCTL for VM_BIND is not a requirement to get -Xe merged, it is mandatory to have a consensus with other drivers and Mesa. -It needs to be clear how to handle async VM_BIND and interactions with userspace -memory fences. Ideally with helper support so people don't get it wrong in all -possible ways. - -As a key measurable result, the benefits of ASYNC VM_BIND and a discussion of -various flavors, error handling and sample API suggestions are documented in -:doc:`The ASYNC VM_BIND document </gpu/drm-vm-bind-async>`. - -Drm_scheduler -------------- -Xe primarily uses Firmware based scheduling (GuC FW). However, it will use -drm_scheduler as the scheduler ‘frontend’ for userspace submission in order to -resolve syncobj and dma-buf implicit sync dependencies. However, drm_scheduler is -not yet prepared to handle the 1-to-1 relationship between drm_gpu_scheduler and -drm_sched_entity. - -Deeper changes to drm_scheduler should *not* be required to get Xe accepted, but -some consensus needs to be reached between Xe and other community drivers that -could also benefit from this work, for coupling FW based/assisted submission such -as the ARM’s new Mali GPU driver, and others. - -As a key measurable result, the patch series introducing Xe itself shall not -depend on any other patch touching drm_scheduler itself that was not yet merged -through drm-misc. This, by itself, already includes the reach of an agreement for -uniform 1 to 1 relationship implementation / usage across drivers. - -Long running compute: minimal data structure/scaffolding --------------------------------------------------------- -The generic scheduler code needs to include the handling of endless compute -contexts, with the minimal scaffolding for preempt-ctx fences (probably on the -drm_sched_entity) and making sure drm_scheduler can cope with the lack of job -completion fence. - -The goal is to achieve a consensus ahead of Xe initial pull-request, ideally with -this minimal drm/scheduler work, if needed, merged to drm-misc in a way that any -drm driver, including Xe, could re-use and add their own individual needs on top -in a next stage. However, this should not block the initial merge. - -Dev_coredump ------------- - -Xe needs to align with other drivers on the way that the error states are -dumped, avoiding a Xe only error_state solution. The goal is to use devcoredump -infrastructure to report error states, since it produces a standardized way -by exposing a virtual and temporary /sys/class/devcoredump device. - -As the key measurable result, Xe driver needs to provide GPU snapshots captured -at hang time through devcoredump, but without depending on any core modification -of devcoredump infrastructure itself. - -Later, when we are in-tree, the goal is to collaborate with devcoredump -infrastructure with overall possible improvements, like multiple file support -for better organization of the dumps, snapshot support, dmesg extra print, -and whatever may make sense and help the overall infrastructure. - -DRM_VM_BIND ------------ -Nouveau, and Xe are all implementing ‘VM_BIND’ and new ‘Exec’ uAPIs in order to -fulfill the needs of the modern uAPI. Xe merge should *not* be blocked on the -development of a common new drm_infrastructure. However, the Xe team needs to -engage with the community to explore the options of a common API. - -As a key measurable result, the DRM_VM_BIND needs to be documented in this file -below, or this entire block deleted if the consensus is for independent drivers -vm_bind ioctls. - -Although having a common DRM level IOCTL for VM_BIND is not a requirement to get -Xe merged, it is mandatory to enforce the overall locking scheme for all major -structs and list (so vm and vma). So, a consensus is needed, and possibly some -common helpers. If helpers are needed, they should be also documented in this -document. - -GPU VA ------- -Two main goals of Xe are meeting together here: - -1) Have an uAPI that aligns with modern UMD needs. - -2) Early upstream engagement. - -RedHat engineers working on Nouveau proposed a new DRM feature to handle keeping -track of GPU virtual address mappings. This is still not merged upstream, but -this aligns very well with our goals and with our VM_BIND. The engagement with -upstream and the port of Xe towards GPUVA is already ongoing. - -As a key measurable result, Xe needs to be aligned with the GPU VA and working in -our tree. Missing Nouveau patches should *not* block Xe and any needed GPUVA -related patch should be independent and present on dri-devel or acked by -maintainers to go along with the first Xe pull request towards drm-next. |