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arm64: mm: Preserve existing table mappings when mapping DRAM

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Instead of blindly overwriting an existing table entry when mapping DRAM
regions, take care not to replace a pre-existing table entry with a
block entry. This permits the logic of mapping the kernel's linear alias
to be simplified in a subsequent patch.

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel 2026-05-29 17:01:55 +02:00 committed by Will Deacon
parent 8dd640d923
commit a64293e993
1 changed files with 4 additions and 2 deletions
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6
arch/arm64/mm/mmu.c
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@ -256,7 +256,8 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
/* try section mapping first */
if (((addr | next | phys) & ~PMD_MASK) == 0 &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
(flags & NO_BLOCK_MAPPINGS) == 0 &&
!pmd_table(old_pmd)) {
WARN_ON(!pmd_set_huge(pmdp, phys, prot));
/*
@ -379,7 +380,8 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
*/
if (pud_sect_supported() &&
((addr | next | phys) & ~PUD_MASK) == 0 &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
(flags & NO_BLOCK_MAPPINGS) == 0 &&
!pud_table(old_pud)) {
WARN_ON(!pud_set_huge(pudp, phys, prot));
/*