fix(core): restore access descriptors when a VMM grow rolls back - #2440
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aryanputta wants to merge 2 commits into
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fix(core): restore access descriptors when a VMM grow rolls back#2440aryanputta wants to merge 2 commits into
aryanputta wants to merge 2 commits into
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The slow-path rollback in modify_allocation remapped the old physical memory to its original address but never reapplied the access descriptors that the preceding unmap dropped, so a buffer recovered by a failed grow faulted on its next access until cuMemSetAccess was run again. Hoist the descriptor list above the transaction so the rollback applies the same descriptors the forward path does, and reapply them to the old range after the remap succeeds. Defect 1 of NVIDIA#2388. Signed-off-by: Aryan <aryansputta@gmail.com>
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Signed-off-by: Aryan <aryansputta@gmail.com>
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Description
Defect 1 of #2388, continuing the per-defect split from #2407 (defect 2) and #2418 (defect 4).
_grow_allocation_slow_path()unmaps the old VA range before remapping the physical memory into the new reservation. Access permissions live on the mapping, so that unmap drops the resource's access descriptors. The_remap_oldrollback restored the mapping but not the descriptors, so a buffer recovered from a failed grow was mapped and yet not accessible: it faulted on its next access untilcuMemSetAccesswas run again._remap_oldnow reapplies the access descriptors to the old range after the remap succeeds. It stays inside the same best-efforttry, so a failure while restoring access cannot mask the error that triggered the rollback.The descriptor list is now built once above the transaction and shared by the forward path and the rollback, rather than built only at the point of use near the end. The rollback restores exactly the descriptors the grow was in the middle of applying, and there is one source of truth for them.
Test
test_vmm_allocator_grow_slow_path_rollback_restores_accessfailscuMemSetAccessover the new range to drive the transaction into rollback, then asserts that the old range is remapped, that its access is reapplied, that the two happen in that order, and that the failed reservation is still freed. Reverting the three added lines fails the test on the restored-access assertion.Checks
ruff check,ruff formatmypy-cuda-corecython-lint,stubgen-pyxlychee, SPDX headers, rst hooks