On Wed, Jan 10, 2024 at 02:07:38PM -0600, Lucas De Marchi wrote: > On Wed, Jan 10, 2024 at 02:04:27PM -0500, Rodrigo Vivi wrote: > > The last TODO item here that was not marked as done was > > the display portion, which came along with the pull-request. > > > > So, now that Xe is part of drm-next and it includes the > > display portion, let's entirely kill this RFC here. > > > > Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> > > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > > Cc: Oded Gabbay <ogabbay@xxxxxxxxxx> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> > > > Acked-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> Thanks, pushed to drm-misc-next. > > thanks > Lucas De Marchi > > > --- > > Documentation/gpu/rfc/xe.rst | 234 ----------------------------------- > > 1 file changed, 234 deletions(-) > > delete mode 100644 Documentation/gpu/rfc/xe.rst > > > > diff --git a/Documentation/gpu/rfc/xe.rst b/Documentation/gpu/rfc/xe.rst > > deleted file mode 100644 > > index 97cf87578f97..000000000000 > > --- 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. > > -- > > 2.43.0 > >
