This is the third 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.
Patches 1 & 2 are new for v3 and refactor the existing migration and device private entry functions.
Patches 3 & 4 rework try_to_unmap_one() by splitting out unrelated functionality into separate functions - try_to_migrate_one() and try_to_munlock_one(). These should not change any functionality, but any help testing would be much appreciated as I have not been able to test every single usage of try_to_unmap_one().
Patch 5 contains the bulk of the implementation for device exclusive memory.
Patch 6 contains some additions to the HMM selftests to ensure everything works as expected and has not changed significantly since v2.
Patch 7 was posted previously and has not changed.
Patch 8 was posted for v2 and has not changed significantly.
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.
v3: * Refactored some existing functionality. * Switched to using get_user_pages_remote() instead of open-coding it. * Moved code out of hmm.
v2: * Changed implementation to use special swap entries instead of device private pages.
Alistair Popple (8): mm: Remove special swap entry functions mm/swapops: Rework swap entry manipulation code mm/rmap: Split try_to_munlock from try_to_unmap mm/rmap: Split migration into its own function mm: Device exclusive memory access mm: Selftests for exclusive device memory nouveau/svm: Refactor nouveau_range_fault nouveau/svm: Implement atomic SVM access
Documentation/vm/hmm.rst | 15 + arch/s390/mm/pgtable.c | 2 +- drivers/gpu/drm/nouveau/include/nvif/if000c.h | 1 + drivers/gpu/drm/nouveau/nouveau_svm.c | 120 +++- drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.h | 1 + .../drm/nouveau/nvkm/subdev/mmu/vmmgp100.c | 6 + fs/proc/task_mmu.c | 23 +- include/linux/rmap.h | 8 +- include/linux/swap.h | 8 +- include/linux/swapops.h | 105 ++-- lib/test_hmm.c | 124 ++++ lib/test_hmm_uapi.h | 2 + mm/debug_vm_pgtable.c | 12 +- mm/hmm.c | 12 +- mm/huge_memory.c | 36 +- mm/hugetlb.c | 10 +- mm/memcontrol.c | 2 +- mm/memory.c | 128 +++- mm/migrate.c | 41 +- mm/mprotect.c | 18 +- mm/page_vma_mapped.c | 15 +- mm/rmap.c | 558 +++++++++++++++--- tools/testing/selftests/vm/hmm-tests.c | 219 +++++++ 23 files changed, 1207 insertions(+), 259 deletions(-)