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>

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 6ac0086..7b387c3 100644 (file)
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -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.

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7f361bc..53126a3 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -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

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 9b4fc78..63732ca 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -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;