tree: https://gitee.com/openeuler/kernel.git OLK-6.6 head: dfb9bd9242c2350c127d51a126976ed386e9cc48 commit: 3a1e43e597d3d6f872dd786af8dad22947c8239a [3269/3269] zcopy: Add ZCOPY documentation reproduce: (https://download.01.org/0day-ci/archive/20251120/202511200347.5qevtABT-lkp@i...) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202511200347.5qevtABT-lkp@intel.com/ All warnings (new ones prefixed by >>): WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 -function HID quirks ./include/linux/hid.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/i2c-atr.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 -internal ./include/linux/mutex.h' failed with return code 2 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 -function klp_patch -function klp_object -function klp_func -function klp_callbacks -function klp_state ./include/linux/livepatch.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/seqlock.h' failed with return code 1

...

Documentation/misc-devices/zcopy.rst:18: WARNING: Title underline too short. -- Key features ----------- [docutils] Documentation/misc-devices/zcopy.rst:18: WARNING: Title underline too short. -- WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/fprobe.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 -internal ./include/linux/mutex.h' failed with return code 2 Documentation/translations/zh_TW/dev-tools/index.rst:21: WARNING: toctree contains reference to nonexisting document 'translations/zh_TW/dev-tools/sparse' [toc.not_readable] WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/fwctl.h' failed with return code 1 Documentation/arch/x86/hygon-secure-virtualization.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/misc-devices/zcopy.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/mm/dynamic_hugetlb.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/networking/device_drivers/ethernet/nebula-matrix/m18120.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/networking/hinic3.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/scsi/hisi_raid.rst: WARNING: document isn't included in any toctree [toc.not_included] Documentation/scsi/sssraid.rst: WARNING: document isn't included in any toctree [toc.not_included] -- Important constraints and requirements --------------------- [docutils] Documentation/misc-devices/zcopy.rst:61: ERROR: Unexpected indentation. [docutils] Documentation/misc-devices/zcopy.rst:58: WARNING: Inline emphasis start-string without end-string. [docutils] Documentation/misc-devices/zcopy.rst:61: WARNING: Inline emphasis start-string without end-string. [docutils] Documentation/misc-devices/zcopy.rst:64: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils] WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/damon.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/highmem.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/highmem-internal.h' failed with return code 1 WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 8.2.3 ./include/linux/migrate.h' failed with return code 1 Documentation/networking/device_drivers/ethernet/3snic/sssnic.rst:42: WARNING: Enumerated list ends without a blank line; unexpected unindent. [docutils]

vim +18 Documentation/misc-devices/zcopy.rst 15 16 17 Key features

18 ----------- 19 - Supports zero-copy communication between intra-node processes. 20 - Handles both PTE-level small pages and PMD-level huge pages. 21 - Preserves the read/write permissions of the source page in the target address space. 22 23 24 Important constraints and requirements 25 --------------------- 26 1. Callers must ensure the source address is already mapped to physical pages, 27 while the destination address is unused (no existing mappings). If exists 28 old mappings, the return value is -EAGAIN. For this case, caller should free 29 the old dst_addr, and alloc a new one to try again. 30 31 2. No internal locking is implemented in the PageAttach interface; Callers 32 must manage memory mapping and release order to avoid race conditions. 33 34 3. Source and destination must be different processes (not threads of the same process). 35 36 4. Only user-space addresses are supported; kernel addresses cannot be mapped. 37 38 5. Both source and destination processes must remain alive during the mapping operation. 39 40 6. PUD-level huge pages are not supported in current implementation. 41 42 7. The start address and size of both source and destination must be PMD-size-aligned. 43 44 8. Callers are responsible for ensuring safe access to mapped pages after attachment, 45 as permissions are inherited from the source. 46 47 48 Use 49 --- 50 Process a 51 src_addr= aligned_alloc(ALIGN_SIZE_2M, size); 52 memset(src_addr, 0, size); 53 54 Process b 55 #define ALIGN_SIZE_2M 2097152 56 int fd = open(SLS_DEVICE, O_RDWR); 57 58 dst_addr= aligned_alloc(ALIGN_SIZE_2M, size); 59 res = zcopy(fd, (void *)src_addr, dst_addr, src_pid, dst_pid, size); 60 while(res.ret == -EAGAIN && retry--) { 61 free(dst_addr); 62 dst_addr= aligned_alloc(ALIGN_SIZE_2M, size); 63 res = zcopy(fd, (void *)src_addr, dst_addr, src_pid, dst_pid, aligned_size); 64 }

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