This is the second version of a series to add support to Nouveau for atomic memory operations on OpenCL shared virtual memory (SVM) regions. This is achieved using the atomic PTE bits on the GPU to only permit atomic operations to system memory when a page is not mapped in userspace on the CPU. The previous version of this series used an unmap and pin page migration, however this resulted in problems with ZONE_MOVABLE and other issues so this series uses a different approach.
Instead exclusive device access is implemented by adding a new swap entry type (SWAP_DEVICE_EXCLUSIVE) which is similar to a migration entry. The main difference is that on fault the original entry is immediately restored by the fault handler instead of waiting.
Restoring the entry triggers calls to MMU notifers which allows a device driver to revoke the atomic access permission from the GPU prior to the CPU finalising the entry.
Patch 1 contains the bulk of the memory management changes required to implement the new entry type.
Patch 2 contains some additions to the HMM selftests to ensure everything works as expected.
Patch 3 was posted previously and has not changed.
Patch 4 is similar to what was posted previously but updated to use the new swap entries instread of migration.
This has been tested using the latest upstream Mesa userspace with a simple OpenCL test program which checks the results of atomic GPU operations on a SVM buffer whilst also writing to the same buffer from the CPU.
Alistair Popple (4): hmm: Device exclusive memory access hmm: Selftests for exclusive device memory nouveau/svm: Refactor nouveau_range_fault nouveau/svm: Implement atomic SVM access
Documentation/vm/hmm.rst | 15 ++ drivers/gpu/drm/nouveau/include/nvif/if000c.h | 1 + drivers/gpu/drm/nouveau/nouveau_svm.c | 118 +++++++--- drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.h | 1 + .../drm/nouveau/nvkm/subdev/mmu/vmmgp100.c | 6 + fs/proc/task_mmu.c | 7 + include/linux/hmm.h | 4 + include/linux/rmap.h | 1 + include/linux/swap.h | 10 +- include/linux/swapops.h | 32 +++ lib/test_hmm.c | 124 ++++++++++ lib/test_hmm_uapi.h | 2 + mm/hmm.c | 206 ++++++++++++++++ mm/memory.c | 34 ++- mm/mprotect.c | 7 + mm/page_vma_mapped.c | 14 +- mm/rmap.c | 29 ++- tools/testing/selftests/vm/hmm-tests.c | 219 ++++++++++++++++++ 18 files changed, 792 insertions(+), 38 deletions(-)