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Revert the HUGETLB_PAGE_FREE_VMEMMAP selection from commit1e63ac088f("arm64: mm: hugetlb: enable HUGETLB_PAGE_FREE_VMEMMAP for arm64") but keep the flush_dcache_page() compound_head() change as it aligns with the corresponding check in the __sync_icache_dcache() function. The original config option was renamed in commit47010c040d("mm: hugetlb_vmemmap: cleanup CONFIG_HUGETLB_PAGE_FREE_VMEMMAP*") to HUGETLB_PAGE_OPTIMIZE_VMEMMAP and the flush_dcache_page() check was further simplified by commit2da1c30929("mm: hugetlb_vmemmap: delete hugetlb_optimize_vmemmap_enabled()"). The reason for the revert is that the generic vmemmap_remap_pte() function changes both the permissions (writeable to read-only) and the output address (pfn) of the vmemmap ptes. This is deemed UNPREDICTABLE by the Arm architecture without a break-before-make sequence (make the PTE invalid, TLBI, write the new valid PTE). However, such sequence is not possible since the vmemmap may be concurrently accessed by the kernel. Disable the optimisation until a better solution is found. Fixes:1e63ac088f("arm64: mm: hugetlb: enable HUGETLB_PAGE_FREE_VMEMMAP for arm64") Cc: <stable@vger.kernel.org> # 5.19.x Cc: Muchun Song <muchun.song@linux.dev> Cc: Will Deacon <will@kernel.org> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Link: https://lore.kernel.org/r/Y9pZALdn3pKiJUeQ@arm.com Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Link: https://lore.kernel.org/r/20230222175232.540851-1-catalin.marinas@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.