Commit 218564b1 authored Nov 05, 2019 by Bhupesh Sharma Committed by Catalin Marinas Nov 06, 2019

arm64: mm: Remove MAX_USER_VA_BITS definition



commit 9b31cf49 ("arm64: mm: Introduce MAX_USER_VA_BITS definition")
introduced the MAX_USER_VA_BITS definition, which was used to support
the arm64 mm use-cases where the user-space could use 52-bit virtual
addresses whereas the kernel-space would still could a maximum of 48-bit
virtual addressing.

But, now with commit b6d00d47 ("arm64: mm: Introduce 52-bit Kernel
VAs"), we removed the 52-bit user/48-bit kernel kconfig option and hence
there is no longer any scenario where user VA != kernel VA size
(even with CONFIG_ARM64_FORCE_52BIT enabled, the same is true).

Hence we can do away with the MAX_USER_VA_BITS macro as it is equal to
VA_BITS (maximum VA space size) in all possible use-cases. Note that
even though the 'vabits_actual' value would be 48 for arm64 hardware
which don't support LVA-8.2 extension (even when CONFIG_ARM64_VA_BITS_52
is enabled), VA_BITS would still be set to a value 52. Hence this change
would be safe in all possible VA address space combinations.

Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 32d18708

arch/arm64/include/asm/memory.h

+0 −6

Original line number	Diff line number	Diff line
		@@ -69,12 +69,6 @@
		#define KERNEL_START _text
		#define KERNEL_END _end

		#ifdef CONFIG_ARM64_VA_BITS_52
		#define MAX_USER_VA_BITS 52
		#else
		#define MAX_USER_VA_BITS VA_BITS
		#endif

		/*
		* Generic and tag-based KASAN require 1/8th and 1/16th of the kernel virtual
		* address space for the shadow region respectively. They can bloat the stack

arch/arm64/include/asm/pgtable-hwdef.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -69,7 +69,7 @@
		#define PGDIR_SHIFT ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - CONFIG_PGTABLE_LEVELS)
		#define PGDIR_SIZE (_AC(1, UL) << PGDIR_SHIFT)
		#define PGDIR_MASK (~(PGDIR_SIZE-1))
		#define PTRS_PER_PGD (1 << (MAX_USER_VA_BITS - PGDIR_SHIFT))
		#define PTRS_PER_PGD (1 << (VA_BITS - PGDIR_SHIFT))

		/*
		* Section address mask and size definitions.

arch/arm64/include/asm/processor.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -9,7 +9,7 @@
		#define __ASM_PROCESSOR_H

		#define KERNEL_DS UL(-1)
		#define USER_DS ((UL(1) << MAX_USER_VA_BITS) - 1)
		#define USER_DS ((UL(1) << VA_BITS) - 1)

		/*
		* On arm64 systems, unaligned accesses by the CPU are cheap, and so there is

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