arm64: mm: Preserve non-contiguous descriptors when mapping DRAM

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Instead of blindly overwriting existing live entries regardless of the
value of their contiguous bit when mapping DRAM regions at
contiguous-hint granularity, check whether the contiguous region in
question contains any valid descriptors that have the contiguous bit
cleared, and in that case, leave the contiguous bit unset on the entire
region. This permits the logic of mapping the kernel's linear alias to
be simplified in a subsequent patch.

Note that this can only result in a misprogrammed contiguous bit (as per
ARM ARM RNGLXZ) if the region in question already contains a mix of
valid contiguous and valid non-contiguous descriptors, in which case it
was already misprogrammed to begin with.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

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Ard Biesheuvel 2026-05-29 17:01:56 +02:00 • committed by Will Deacon

parent a64293e993

commit ecda73ae92

2 changed files with 24 additions and 2 deletions

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4

arch/arm64/include/asm/pgtable.h

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22

arch/arm64/mm/mmu.c

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