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It has become apparent that one has to take special care when modifying attributes of memory mappings that employ the contiguous bit. Both the requirement and the architecturally correct "Break-Before-Make" technique of updating contiguous entries can be found described in: ARM DDI 0487A.k_iss10775, "Misprogramming of the Contiguous bit", page D4-1762. The huge pte accessors currently replace the attributes of contiguous pte entries in place thus can, on certain platforms, lead to TLB conflict aborts or even erroneous results returned from TLB lookups. This patch adds two helper functions - * get_clear_flush(.) - clears a contiguous entry and returns the head pte (whilst taking care to retain dirty bit information that could have been modified by DBM). * clear_flush(.) that clears a contiguous entry A tlb invalidate is performed to then ensure that there is no possibility of multiple tlb entries being present for the same region. Cc: David Woods <dwoods@mellanox.com> Signed-off-by: Steve Capper <steve.capper@arm.com> (Added helper clear_flush(), updated commit log, and some cleanup) Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> [catalin.marinas@arm.com: remove CONFIG_ARM64_HW_AFDBM check] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.