On Tue, 9 Dec 2025 14:41:57 +0100 Thomas Zimmermann <[email protected]> wrote:
> Duplicate GEM-SHMEM to GEM-UMA. Convert all DRM drivers for UMA > systems if they currently use GEM-SHMEM. > > Many DRM drivers for hardware with Unified Memory Architecture (UMA) > currently builds upon GEM-SHMEM and extends the helpers with features > for managing the GPU MMU. This allows the GPU to access the GEM buffer > content for its operation. > > There is another, larger, set of DRM drivers that use GEM-SHMEM merely > as buffer management with no hardware support. These drivers copy the > buffer content to the GPU on each page flip. The GPU itself has no direct > access. Hardware of this type is usually in servers, behind slow busses > (SPI, USB), or provided by firmware (drivers in sysfb/). > > After some discussion with Boris on the future of GEM-SHMEM, it seems > to me that both use cases more and more diverge from each other. The > most prominent example is the implementation of gem_prime_import, > where both use cases use distinct approaches. > > So we discussed the introduction of a GEM-UMA helper library for > UMA-based hardware. GEM-UMA will remain flexible enough for drivers > to extend it for their use case. GEM-SHMEM will become focused on the > simple-hardware use case. The benefit for both libraries is that they > will be easier to understand and maintain. GEM-SHMEM can be simplified > signiifcantly, I think. > > This RFC series introduces GEM-UMA and converts the UMA-related drivers. > > Patches 1 and 2 fix issues in GEM-SHMEM, so that we don't duplicate > errornous code. > > Patch 3 copies GEM-SHMEM to GEM-UMA. Patch 4 then does soem obvious > cleanups of unnecessary code. Instead of copying the code as-is, I'd rather take a step back and think about what we need and how we want to handle more complex stuff, like reclaim. I've started working on a shrinker for panthor [1], and as part of this series, I've added a commit implementing just enough to replace what gem-shmem currently provides. Feels like the new GEM-UMA thing could be designed on a composition rather than inheritance model, where we have sub-components (backing, cpu_map, gpu_map) that can be pulled in and re-used by the driver implementation. The common helpers would take those sub-components instead of a plain GEM object. That would leave the drivers free of how their internal gem_object fields are laid out and wouldn't require overloading the ->gem_create_object() function. It seems to be that it would better match the model you were describing the other day. > > Patches 5 to 13 update the drivers that can be converted to GEM-UMA. > These changes are just symbol renaming. There are so far no functional > differences between the memory managers. > > A gave GEM-UMA some smoke testing by running virtgpu. [1]https://gitlab.freedesktop.org/bbrezillon/linux/-/commits/panthor-shrinker-revisited/drivers?ref_type=heads [2]https://gitlab.freedesktop.org/bbrezillon/linux/-/commit/4e6927fc2c60265b77a5a88013f55377bc4f4ab3 > > Thomas Zimmermann (13): > drm/gem-shmem: Fix typos in documentation > drm/gem-shmem: Fix the MODULE_LICENSE() string > drm: Add GEM-UMA helpers for memory management > drm/gem-uma: Remove unused interfaces > drm/imagination: Use GEM-UMA helpers for memory management > drm/lima: Use GEM-UMA helpers for memory management > drm/panfrost: Use GEM-UMA helpers for memory management > drm/panthor: Use GEM-UMA helpers for memory management > drm/v3d: Use GEM-UMA helpers for memory management > drm/virtgpu: Use GEM-UMA helpers for memory management > accel/amdxdna: Use GEM-UMA helpers for memory management > accel/ivpu: Use GEM-UMA helpers for memory management > accel/rocket: Use GEM-UMA helpers for memory management > > Documentation/gpu/drm-mm.rst | 12 + > drivers/accel/amdxdna/Kconfig | 2 +- > drivers/accel/amdxdna/aie2_ctx.c | 1 - > drivers/accel/amdxdna/aie2_message.c | 1 - > drivers/accel/amdxdna/aie2_pci.c | 1 - > drivers/accel/amdxdna/aie2_psp.c | 1 - > drivers/accel/amdxdna/aie2_smu.c | 1 - > drivers/accel/amdxdna/amdxdna_ctx.c | 7 +- > drivers/accel/amdxdna/amdxdna_gem.c | 49 +- > drivers/accel/amdxdna/amdxdna_gem.h | 5 +- > .../accel/amdxdna/amdxdna_mailbox_helper.c | 1 - > drivers/accel/amdxdna/amdxdna_pci_drv.c | 1 - > drivers/accel/amdxdna/amdxdna_sysfs.c | 1 - > drivers/accel/ivpu/Kconfig | 2 +- > drivers/accel/ivpu/ivpu_gem.c | 36 +- > drivers/accel/ivpu/ivpu_gem.h | 4 +- > drivers/accel/rocket/Kconfig | 2 +- > drivers/accel/rocket/rocket_gem.c | 46 +- > drivers/accel/rocket/rocket_gem.h | 6 +- > drivers/gpu/drm/Kconfig | 9 + > drivers/gpu/drm/Kconfig.debug | 1 + > drivers/gpu/drm/Makefile | 4 + > drivers/gpu/drm/drm_fbdev_uma.c | 203 +++++ > drivers/gpu/drm/drm_gem_shmem_helper.c | 5 +- > drivers/gpu/drm/drm_gem_uma_helper.c | 787 ++++++++++++++++++ > drivers/gpu/drm/imagination/Kconfig | 4 +- > drivers/gpu/drm/imagination/pvr_drv.c | 2 +- > drivers/gpu/drm/imagination/pvr_free_list.c | 2 +- > drivers/gpu/drm/imagination/pvr_gem.c | 74 +- > drivers/gpu/drm/imagination/pvr_gem.h | 12 +- > drivers/gpu/drm/lima/Kconfig | 4 +- > drivers/gpu/drm/lima/lima_drv.c | 2 +- > drivers/gpu/drm/lima/lima_gem.c | 30 +- > drivers/gpu/drm/lima/lima_gem.h | 6 +- > drivers/gpu/drm/panfrost/Kconfig | 2 +- > drivers/gpu/drm/panfrost/panfrost_drv.c | 2 +- > drivers/gpu/drm/panfrost/panfrost_gem.c | 30 +- > drivers/gpu/drm/panfrost/panfrost_gem.h | 6 +- > .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 30 +- > drivers/gpu/drm/panfrost/panfrost_mmu.c | 8 +- > drivers/gpu/drm/panfrost/panfrost_perfcnt.c | 6 +- > drivers/gpu/drm/panthor/Kconfig | 2 +- > drivers/gpu/drm/panthor/panthor_drv.c | 2 +- > drivers/gpu/drm/panthor/panthor_fw.c | 4 +- > drivers/gpu/drm/panthor/panthor_gem.c | 40 +- > drivers/gpu/drm/panthor/panthor_gem.h | 8 +- > drivers/gpu/drm/panthor/panthor_mmu.c | 10 +- > drivers/gpu/drm/panthor/panthor_sched.c | 1 - > drivers/gpu/drm/tests/Makefile | 1 + > drivers/gpu/drm/tests/drm_gem_uma_test.c | 385 +++++++++ > drivers/gpu/drm/v3d/Kconfig | 2 +- > drivers/gpu/drm/v3d/v3d_bo.c | 45 +- > drivers/gpu/drm/v3d/v3d_drv.h | 4 +- > drivers/gpu/drm/v3d/v3d_mmu.c | 9 +- > drivers/gpu/drm/virtio/Kconfig | 4 +- > drivers/gpu/drm/virtio/virtgpu_drv.c | 4 +- > drivers/gpu/drm/virtio/virtgpu_drv.h | 12 +- > drivers/gpu/drm/virtio/virtgpu_object.c | 64 +- > drivers/gpu/drm/virtio/virtgpu_plane.c | 6 +- > drivers/gpu/drm/virtio/virtgpu_vq.c | 6 +- > include/drm/drm_fbdev_uma.h | 20 + > include/drm/drm_gem_uma_helper.h | 293 +++++++ > 62 files changed, 2018 insertions(+), 312 deletions(-) > create mode 100644 drivers/gpu/drm/drm_fbdev_uma.c > create mode 100644 drivers/gpu/drm/drm_gem_uma_helper.c > create mode 100644 drivers/gpu/drm/tests/drm_gem_uma_test.c > create mode 100644 include/drm/drm_fbdev_uma.h > create mode 100644 include/drm/drm_gem_uma_helper.h > > > base-commit: 0a21e96e0b6840d2a4e0b45a957679eeddeb4362 > prerequisite-patch-id: c67e5d886a47b7d0266d81100837557fda34cb24 > prerequisite-patch-id: a5a973e527c88a5b47053d7a72aefe0b550197cb > prerequisite-patch-id: 719d09751d38f5da743beed6266585ee063e1e29 > prerequisite-patch-id: 0bbc85bc6b528c32592e07f4ceafa51795c4cad9 > prerequisite-patch-id: c856d9c8a026e3244c44ec829e426e0ad4a685ab > prerequisite-patch-id: 13441c9ed3062ae1448a53086559dfcbbd578177 > prerequisite-patch-id: 951c039657c1f58e4b6e36bc01c7a1c69ed59767 > prerequisite-patch-id: 4370b8b803ca439666fb9d2beb862f6e78347ce3 > prerequisite-patch-id: ebbaad226ed599f7aad4784fb3f4aaebe34cb110 > prerequisite-patch-id: cb907c3e3e14de7f4d13b429f3a2a88621a8a9fe > prerequisite-patch-id: 0e243b426742122b239af59e36d742da5795a8b1 > prerequisite-patch-id: 120f97fa1af9891375a0dcf52c51c1907b01fe6a
