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arm64: head: drop idmap_ptrs_per_pgd 

The assignment of idmap_ptrs_per_pgd lacks any cache invalidation, even
though it is updated with the MMU and caches disabled. However, we never
bother to read the value again except in the very next instruction, and
so we can just drop the variable entirely.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220624150651.1358849-5-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel 2022-06-24 17:06:34 +02:00 committed by Will Deacon
parent e8d13cced5
commit ebd9aea1f2
3 changed files with 3 additions and 6 deletions
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1
arch/arm64/include/asm/mmu_context.h
View File

@ -61,7 +61,6 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
* physical memory, in which case it will be smaller.
*/
extern int idmap_t0sz;
extern u64 idmap_ptrs_per_pgd;
/*
* Ensure TCR.T0SZ is set to the provided value.

7
arch/arm64/kernel/head.S
View File

@ -300,6 +300,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
* range in that case, and configure an additional translation level
* if needed.
*/
mov x4, #PTRS_PER_PGD
idmap_get_t0sz x5
cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
b.ge 1f // .. then skip VA range extension
@ -319,18 +320,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
#error "Mismatch between VA_BITS and page size/number of translation levels"
#endif
mov x4, EXTRA_PTRS
create_table_entry x0, x3, EXTRA_SHIFT, x4, x5, x6
mov x2, EXTRA_PTRS
create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
#else
/*
* If VA_BITS == 48, we don't have to configure an additional
* translation level, but the top-level table has more entries.
*/
mov x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
str_l x4, idmap_ptrs_per_pgd, x5
#endif
1:
ldr_l x4, idmap_ptrs_per_pgd
adr_l x6, __idmap_text_end // __pa(__idmap_text_end)
map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14

1
arch/arm64/mm/mmu.c
View File

@ -44,7 +44,6 @@
#define NO_EXEC_MAPPINGS BIT(2) /* assumes FEAT_HPDS is not used */
int idmap_t0sz __ro_after_init;
u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
#if VA_BITS > 48
u64 vabits_actual __ro_after_init = VA_BITS_MIN;