[PATCH 3/5] arm64: mm: use a compile time constant for vabits_actual when possible
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2021-03-10 17:17:05
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
The size of the kernel VA space is a compile time constant unless the kernel is built to support 52-bit virtual addressing, which today is only supported on 64k page size kernels (although this has recently changed in the architecture). This means that in many configurations, vabits_actual can never deviate from its build time default, making it rather pointless to carry this value in a variable. So use a compile time constant for vabits_actual unless it can really assume different values. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm64/include/asm/memory.h | 4 ++++ arch/arm64/kernel/head.S | 12 ++++++------ arch/arm64/mm/mmu.c | 2 ++ 3 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index c759faf7a1ff..501c5c87ec0a 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h@@ -179,7 +179,11 @@ #include <linux/types.h> #include <asm/bug.h> +#ifdef CONFIG_ARM64_VA_BITS_52 extern u64 vabits_actual; +#else +#define vabits_actual ((u64)VA_BITS) +#endif extern s64 memstart_addr; /* PHYS_OFFSET - the physical address of the start of memory. */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 0b0387644dc0..f65d17a90204 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S@@ -294,16 +294,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables) #ifdef CONFIG_ARM64_VA_BITS_52 mrs_s x6, SYS_ID_AA64MMFR2_EL1 - and x6, x6, #(0xf << ID_AA64MMFR2_LVA_SHIFT) - mov x5, #52 - cbnz x6, 1f -#endif - mov x5, #VA_BITS_MIN -1: + tst x6, #(0xf << ID_AA64MMFR2_LVA_SHIFT) + mov x5, #VA_BITS + mov x6, #VA_BITS_MIN + csel x5, x5, x6, ne + adr_l x6, vabits_actual str x5, [x6] dmb sy dc ivac, x6 // Invalidate potentially stale cache line +#endif /* * VA_BITS may be too small to allow for an ID mapping to be created
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 4c5603c41870..338658cd1bea 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c@@ -43,8 +43,10 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; +#ifdef CONFIG_ARM64_VA_BITS_52 u64 __section(".mmuoff.data.write") vabits_actual; EXPORT_SYMBOL(vabits_actual); +#endif u64 kimage_voffset __ro_after_init; EXPORT_SYMBOL(kimage_voffset);
--
2.30.1
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