Re: [PATCH v3 1/3] riscv: Factorize xip and !xip kernel address conversion macros

Alex Ghiti
2021-06-03T12:58:16Z

Hi Jisheng,

Le 3/06/2021 à 14:27, Jisheng Zhang a écrit :
> On Thu, 3 Jun 2021 10:27:47 +0200
> Alexandre Ghiti <alex@ghiti.fr> wrote:
>
>> To simplify the kernel address conversion code, make the same definition of
>> kernel_mapping_pa_to_va and kernel_mapping_va_to_pa compatible for both xip
>> and !xip kernel by defining XIP_OFFSET to 0 in !xip kernel.
>>
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
>> ---
>> arch/riscv/include/asm/page.h | 14 +++-----------
>> arch/riscv/include/asm/pgtable.h | 2 ++
>> 2 files changed, 5 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
>> index 6a7761c86ec2..6e004d8fda4d 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -93,9 +93,7 @@ extern unsigned long va_pa_offset;
>> #ifdef CONFIG_64BIT
>> extern unsigned long va_kernel_pa_offset;
>> #endif
>> -#ifdef CONFIG_XIP_KERNEL
>> extern unsigned long va_kernel_xip_pa_offset;
>> -#endif
>> extern unsigned long pfn_base;
>> #define ARCH_PFN_OFFSET (pfn_base)
>> #else
>> @@ -103,6 +101,7 @@ extern unsigned long pfn_base;
>> #ifdef CONFIG_64BIT
>> #define va_kernel_pa_offset 0
>> #endif
>> +#define va_kernel_xip_pa_offset 0
>> #define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT)
>> #endif /* CONFIG_MMU */
>>
>> @@ -110,29 +109,22 @@ extern unsigned long kernel_virt_addr;
>>
>> #ifdef CONFIG_64BIT
>> #define linear_mapping_pa_to_va(x) ((void *)((unsigned long)(x) + va_pa_offset))
>> -#ifdef CONFIG_XIP_KERNEL
>> #define kernel_mapping_pa_to_va(y) ({ \
>> unsigned long _y = y; \
>> (_y >= CONFIG_PHYS_RAM_BASE) ?
>
> This CONFIG_PHYS_RAM_BASE is only available for XIP, could result in a
> compiler error for !XIP?

You're right, I have this patch in my branch and forgot to squash it.

>
> I'm also concerned with the unecessary overhead of kernel_mapping_pa_to_va()
> for !XIP case, there's a "if" condition branch, and extra symbol: va_kernel_xip_pa_offset

I understand your concerns even if I don't find that the overhead is
that important here, I prefer the readability improvement. I can always
add unlikely/likely builtin to improve things or completely remove this
patch if others agree with you.

Thanks,

Alex

>
>> (void *)((unsigned long)(_y) + va_kernel_pa_offset + XIP_OFFSET) : \
>> (void *)((unsigned long)(_y) + va_kernel_xip_pa_offset); \
>> })
>> -#else
>> -#define kernel_mapping_pa_to_va(x) ((void *)((unsigned long)(x) + va_kernel_pa_offset))
>> -#endif
>> #define __pa_to_va_nodebug(x) linear_mapping_pa_to_va(x)
>>
>> #define linear_mapping_va_to_pa(x) ((unsigned long)(x) - va_pa_offset)
>> -#ifdef CONFIG_XIP_KERNEL
>> #define kernel_mapping_va_to_pa(y) ({ \
>> unsigned long _y = y; \
>> (_y < kernel_virt_addr + XIP_OFFSET) ? \
>> ((unsigned long)(_y) - va_kernel_xip_pa_offset) : \
>> ((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET); \
>> })
>
> Similar as kernel_mapping_pa_to_va(), an overhead of "if" condition branch
> for !XIP and extra va_kernel_xip_pa_offset symbol.
>
>> -#else
>> -#define kernel_mapping_va_to_pa(x) ((unsigned long)(x) - va_kernel_pa_offset)
>> -#endif
>> +
>> #define __va_to_pa_nodebug(x) ({ \
>> unsigned long _x = x; \
>> (_x < kernel_virt_addr) ? \
>> @@ -141,7 +133,7 @@ extern unsigned long kernel_virt_addr;
>> #else
>> #define __pa_to_va_nodebug(x) ((void *)((unsigned long) (x) + va_pa_offset))
>> #define __va_to_pa_nodebug(x) ((unsigned long)(x) - va_pa_offset)
>> -#endif
>> +#endif /* CONFIG_64BIT */
>>
>> #ifdef CONFIG_DEBUG_VIRTUAL
>> extern phys_addr_t __virt_to_phys(unsigned long x);
>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
>> index bde8ce3bfe7c..d98e931a31e5 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -77,6 +77,8 @@
>>
>> #ifdef CONFIG_XIP_KERNEL
>> #define XIP_OFFSET SZ_8M
>> +#else
>> +#define XIP_OFFSET 0
>> #endif
>>
>> #ifndef __ASSEMBLY__
>
>
>
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