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

Jisheng Zhang
2021-06-03T12:34:59Z

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?

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

> (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__