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arm64: fixmap: Allow 256K early_ioremap() at any offset

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NR_FIX_BTMAPS is the per-slot page limit for early_ioremap(). Since
__early_ioremap() maps the page-aligned physical range, a 256K request
can require one extra page when the physical address is not page-aligned.

Reserve one extra page per slot so the 256K mapping budget is usable
regardless of the initial page offset.

Link: https://lore.kernel.org/r/08fd96fa-ee3a-4904-bd11-bb08bd90436f@kylinos.cn
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Yu Peng 2026-07-08 10:35:14 +08:00 committed by Will Deacon
parent 977f52909c
commit 21fc7ec93f
1 changed files with 5 additions and 1 deletions
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6
arch/arm64/include/asm/fixmap.h
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@ -78,8 +78,12 @@ enum fixed_addresses {
/*
* Temporary boot-time mappings, used by early_ioremap(),
* before ioremap() is functional.
*
* Reserve one extra page so a 256K mapping may start at any
* offset within a page. early_ioremap() maps the page-aligned
* physical range, so the initial offset can consume an extra page.
*/
#define NR_FIX_BTMAPS (SZ_256K / PAGE_SIZE)
#define NR_FIX_BTMAPS ((SZ_256K / PAGE_SIZE) + 1)
#define FIX_BTMAPS_SLOTS 7
#define TOTAL_FIX_BTMAPS (NR_FIX_BTMAPS * FIX_BTMAPS_SLOTS)