Commit a4ee2861 authored by Anshuman Khandual's avatar Anshuman Khandual Committed by Will Deacon
Browse files

arm64/mm: Simplify and document pte_to_phys() for 52 bit addresses 



pte_to_phys() assembly definition does multiple bits field transformations
to derive physical address, embedded inside a page table entry. Unlike its
C counter part i.e __pte_to_phys(), pte_to_phys() is not very apparent. It
simplifies these operations via a new macro PTE_ADDR_HIGH_SHIFT indicating
how far the pte encoded higher address bits need to be left shifted. While
here, this also updates __pte_to_phys() and __phys_to_pte_val().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Suggested-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20221107141753.2938621-1-anshuman.khandual@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent f0c4d9fc

arch/arm64/include/asm/assembler.h

+3 −5
Original line number Diff line number Diff line
@@ -660,12 +660,10 @@ alternative_endif 
	.endm



	.macro	pte_to_phys, phys, pte

#ifdef CONFIG_ARM64_PA_BITS_52

	ubfiz	\phys, \pte, #(48 - 16 - 12), #16

	bfxil	\phys, \pte, #16, #32

	lsl	\phys, \phys, #16

#else

	and	\phys, \pte, #PTE_ADDR_MASK

#ifdef CONFIG_ARM64_PA_BITS_52

	orr	\phys, \phys, \phys, lsl #PTE_ADDR_HIGH_SHIFT

	and	\phys, \phys, GENMASK_ULL(PHYS_MASK_SHIFT - 1, PAGE_SHIFT)

#endif

	.endm

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

+1 −0
Original line number Diff line number Diff line
@@ -159,6 +159,7 @@ 
#ifdef CONFIG_ARM64_PA_BITS_52

#define PTE_ADDR_HIGH		(_AT(pteval_t, 0xf) << 12)

#define PTE_ADDR_MASK		(PTE_ADDR_LOW | PTE_ADDR_HIGH)

#define PTE_ADDR_HIGH_SHIFT	36

#else

#define PTE_ADDR_MASK		PTE_ADDR_LOW

#endif

arch/arm64/include/asm/pgtable.h

+2 −2
Original line number Diff line number Diff line
@@ -77,11 +77,11 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; 
static inline phys_addr_t __pte_to_phys(pte_t pte)

{

	return (pte_val(pte) & PTE_ADDR_LOW) |

		((pte_val(pte) & PTE_ADDR_HIGH) << 36);

		((pte_val(pte) & PTE_ADDR_HIGH) << PTE_ADDR_HIGH_SHIFT);

}

static inline pteval_t __phys_to_pte_val(phys_addr_t phys)

{

	return (phys | (phys >> 36)) & PTE_ADDR_MASK;

	return (phys | (phys >> PTE_ADDR_HIGH_SHIFT)) & PTE_ADDR_MASK;

}

#else

#define __pte_to_phys(pte)	(pte_val(pte) & PTE_ADDR_MASK)