mirror of https://gitee.com/openkylin/linux.git
ARM: Better virt_to_page() handling
virt_to_page() is incredibly inefficient when virt-to-phys patching is
enabled. This is because we end up with this calculation:
page = &mem_map[asm virt_to_phys(addr) >> 12 - __pv_phys_offset >> 12]
in assembly. The asm virt_to_phys() is equivalent this this operation:
addr - PAGE_OFFSET + __pv_phys_offset
and we can see that because this is assembly, the compiler has no chance
to optimise some of that away. This should reduce down to:
page = &mem_map[(addr - PAGE_OFFSET) >> 12]
for the common cases. Permit the compiler to make this optimisation by
giving it more of the information it needs - do this by providing a
virt_to_pfn() macro.
Another issue which makes this more complex is that __pv_phys_offset is
a 64-bit type on all platforms. This is needlessly wasteful - if we
store the physical offset as a PFN, we can save a lot of work having
to deal with 64-bit values, which sometimes ends up producing incredibly
horrid code:
a4c: e3009000 movw r9, #0
a4c: R_ARM_MOVW_ABS_NC __pv_phys_offset
a50: e3409000 movt r9, #0 ; r9 = &__pv_phys_offset
a50: R_ARM_MOVT_ABS __pv_phys_offset
a54: e3002000 movw r2, #0
a54: R_ARM_MOVW_ABS_NC __pv_phys_offset
a58: e3402000 movt r2, #0 ; r2 = &__pv_phys_offset
a58: R_ARM_MOVT_ABS __pv_phys_offset
a5c: e5999004 ldr r9, [r9, #4] ; r9 = high word of __pv_phys_offset
a60: e3001000 movw r1, #0
a60: R_ARM_MOVW_ABS_NC mem_map
a64: e592c000 ldr ip, [r2] ; ip = low word of __pv_phys_offset
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King
parent
83b3f64d46
commit
e26a9e00af
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@ -169,9 +169,17 @@
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* Physical vs virtual RAM address space conversion. These are
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* private definitions which should NOT be used outside memory.h
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* files. Use virt_to_phys/phys_to_virt/__pa/__va instead.
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*
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* PFNs are used to describe any physical page; this means
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* PFN 0 == physical address 0.
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*/
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#ifndef __virt_to_phys
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#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
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#if defined(__virt_to_phys)
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#define PHYS_OFFSET PLAT_PHYS_OFFSET
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#define PHYS_PFN_OFFSET ((unsigned long)(PHYS_OFFSET >> PAGE_SHIFT))
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#define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT)
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#elif defined(CONFIG_ARM_PATCH_PHYS_VIRT)
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/*
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* Constants used to force the right instruction encodings and shifts
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@ -180,12 +188,17 @@
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#define __PV_BITS_31_24 0x81000000
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#define __PV_BITS_7_0 0x81
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extern u64 __pv_phys_offset;
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extern unsigned long __pv_phys_pfn_offset;
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extern u64 __pv_offset;
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extern void fixup_pv_table(const void *, unsigned long);
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extern const void *__pv_table_begin, *__pv_table_end;
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#define PHYS_OFFSET __pv_phys_offset
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#define PHYS_OFFSET ((phys_addr_t)__pv_phys_pfn_offset << PAGE_SHIFT)
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#define PHYS_PFN_OFFSET (__pv_phys_pfn_offset)
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#define virt_to_pfn(kaddr) \
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((((unsigned long)(kaddr) - PAGE_OFFSET) >> PAGE_SHIFT) + \
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PHYS_PFN_OFFSET)
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#define __pv_stub(from,to,instr,type) \
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__asm__("@ __pv_stub\n" \
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@ -246,6 +259,7 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
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#else
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#define PHYS_OFFSET PLAT_PHYS_OFFSET
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#define PHYS_PFN_OFFSET ((unsigned long)(PHYS_OFFSET >> PAGE_SHIFT))
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static inline phys_addr_t __virt_to_phys(unsigned long x)
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{
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@ -257,18 +271,11 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
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return x - PHYS_OFFSET + PAGE_OFFSET;
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}
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#endif
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#endif
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#define virt_to_pfn(kaddr) \
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((((unsigned long)(kaddr) - PAGE_OFFSET) >> PAGE_SHIFT) + \
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PHYS_PFN_OFFSET)
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/*
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* PFNs are used to describe any physical page; this means
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* PFN 0 == physical address 0.
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*
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* This is the PFN of the first RAM page in the kernel
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* direct-mapped view. We assume this is the first page
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* of RAM in the mem_map as well.
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*/
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#define PHYS_PFN_OFFSET ((unsigned long)(PHYS_OFFSET >> PAGE_SHIFT))
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#endif
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/*
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* These are *only* valid on the kernel direct mapped RAM memory.
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@ -346,9 +353,9 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
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*/
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#define ARCH_PFN_OFFSET PHYS_PFN_OFFSET
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#define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
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#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
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#define virt_addr_valid(kaddr) (((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory) \
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&& pfn_valid(__pa(kaddr) >> PAGE_SHIFT) )
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&& pfn_valid(virt_to_pfn(kaddr)))
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#endif
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@ -158,6 +158,6 @@ EXPORT_SYMBOL(__gnu_mcount_nc);
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#endif
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#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
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EXPORT_SYMBOL(__pv_phys_offset);
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EXPORT_SYMBOL(__pv_phys_pfn_offset);
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EXPORT_SYMBOL(__pv_offset);
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#endif
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@ -584,9 +584,10 @@ __fixup_pv_table:
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subs r3, r0, r3 @ PHYS_OFFSET - PAGE_OFFSET
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add r4, r4, r3 @ adjust table start address
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add r5, r5, r3 @ adjust table end address
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add r6, r6, r3 @ adjust __pv_phys_offset address
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add r6, r6, r3 @ adjust __pv_phys_pfn_offset address
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add r7, r7, r3 @ adjust __pv_offset address
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str r8, [r6, #LOW_OFFSET] @ save computed PHYS_OFFSET to __pv_phys_offset
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mov r0, r8, lsr #12 @ convert to PFN
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str r0, [r6, #LOW_OFFSET] @ save computed PHYS_OFFSET to __pv_phys_pfn_offset
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strcc ip, [r7, #HIGH_OFFSET] @ save to __pv_offset high bits
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mov r6, r3, lsr #24 @ constant for add/sub instructions
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teq r3, r6, lsl #24 @ must be 16MiB aligned
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@ -600,7 +601,7 @@ ENDPROC(__fixup_pv_table)
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1: .long .
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.long __pv_table_begin
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.long __pv_table_end
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2: .long __pv_phys_offset
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2: .long __pv_phys_pfn_offset
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.long __pv_offset
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.text
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@ -688,11 +689,11 @@ ENTRY(fixup_pv_table)
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ENDPROC(fixup_pv_table)
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.data
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.globl __pv_phys_offset
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.type __pv_phys_offset, %object
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__pv_phys_offset:
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.quad 0
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.size __pv_phys_offset, . -__pv_phys_offset
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.globl __pv_phys_pfn_offset
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.type __pv_phys_pfn_offset, %object
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__pv_phys_pfn_offset:
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.word 0
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.size __pv_phys_pfn_offset, . -__pv_phys_pfn_offset
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.globl __pv_offset
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.type __pv_offset, %object
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