Messages in this thread |  | | Date | Tue, 5 May 2026 00:23:16 +0000 | | Subject | [RFC PATCH 0/4] dma-mapping: Add preservation of direct allocations | | From | Samiullah Khawaja <> |
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This is an RFC to discuss the preservation of DMA allocations for devices that are using direct allocation mode. Note preservation here means preservation of physical memory only using KHO. IOVAs and IOMMU mappings are out of scope.
The complexity and need of this was discussed in the thread mentioned below. It was proposed to allow preservation of only a subset of allocations with minimum support.
https://lore.kernel.org/all/aepfYzkI7NsVGCF0@google.com/ https://lore.kernel.org/all/aepRy7Gp7Ng85Zr7@willie-the-truck/
Note DMA allocation allows allocation from various allocators in various configurations. This RFC supports preservation with,
- Direct Allocation Only. - Pages allocated through alloc_page (Buddy allocator). - No CMA support. - No DMA allocators.
The changes are also pushed here: https://github.com/samikhawaja/linux/tree/dma-alloc-preserve-direct
Looking forward to your feedback on this.
Thanks
Samiullah Khawaja (4): dma: Add DMA allocation preservation KHO ABI dma/pool: Add an API to check if DMA allocation is from pool dma-direct: Add API to preserve/restore allocations dma-mapping: Add API to preserve/restore DMA allocation
include/linux/dma-direct.h | 29 ++++++ include/linux/dma-map-ops.h | 1 + include/linux/dma-mapping.h | 50 +++++++++ include/linux/kho/abi/dma_alloc.h | 30 ++++++ kernel/dma/Kconfig | 3 + kernel/dma/direct.c | 163 ++++++++++++++++++++++++++++++ kernel/dma/mapping.c | 52 ++++++++++ kernel/dma/pool.c | 13 +++ 8 files changed, 341 insertions(+) create mode 100644 include/linux/kho/abi/dma_alloc.h
base-commit: 9974969c14031a097d6b45bcb7a06bb4aa525c40 prerequisite-patch-id: 41f13f37cb3b439f17dfa4e3f2d5c767aaef0346 -- 2.54.0.545.g6539524ca2-goog
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