Re: [PATCH 1/4] arch: consolidate existing CONFIG_PAGE_SIZE_*KB definitions

[Samuel Holland]

On 2024-02-26 10:14 AM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> These four architectures define the same Kconfig symbols for configuring
> the page size. Move the logic into a common place where it can be shared
> with all other architectures.
> 
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  arch/Kconfig                      | 58 +++++++++++++++++++++++++++++--
>  arch/hexagon/Kconfig              | 25 +++----------
>  arch/hexagon/include/asm/page.h   |  6 +---
>  arch/loongarch/Kconfig            | 21 ++++-------
>  arch/loongarch/include/asm/page.h | 10 +-----
>  arch/mips/Kconfig                 | 58 +++----------------------------
>  arch/mips/include/asm/page.h      | 16 +--------
>  arch/sh/include/asm/page.h        | 13 +------
>  arch/sh/mm/Kconfig                | 42 +++++++---------------
>  9 files changed, 88 insertions(+), 161 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index a5af0edd3eb8..237cea01ed9b 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1078,17 +1078,71 @@ config HAVE_ARCH_COMPAT_MMAP_BASES
>  	  and vice-versa 32-bit applications to call 64-bit mmap().
>  	  Required for applications doing different bitness syscalls.
>  
> +config HAVE_PAGE_SIZE_4KB
> +	bool
> +
> +config HAVE_PAGE_SIZE_8KB
> +	bool
> +
> +config HAVE_PAGE_SIZE_16KB
> +	bool
> +
> +config HAVE_PAGE_SIZE_32KB
> +	bool
> +
> +config HAVE_PAGE_SIZE_64KB
> +	bool
> +
> +config HAVE_PAGE_SIZE_256KB
> +	bool
> +
> +choice
> +	prompt "MMU page size"

Should this have some generic help text (at least a warning about compatibility)?

> +
> +config PAGE_SIZE_4KB
> +	bool "4KB pages"
> +	depends on HAVE_PAGE_SIZE_4KB
> +
> +config PAGE_SIZE_8KB
> +	bool "8KB pages"
> +	depends on HAVE_PAGE_SIZE_8KB
> +
> +config PAGE_SIZE_16KB
> +	bool "16KB pages"
> +	depends on HAVE_PAGE_SIZE_16KB
> +
> +config PAGE_SIZE_32KB
> +	bool "32KB pages"
> +	depends on HAVE_PAGE_SIZE_32KB
> +
> +config PAGE_SIZE_64KB
> +	bool "64KB pages"
> +	depends on HAVE_PAGE_SIZE_64KB
> +
> +config PAGE_SIZE_256KB
> +	bool "256KB pages"
> +	depends on HAVE_PAGE_SIZE_256KB
> +
> +endchoice
> +
>  config PAGE_SIZE_LESS_THAN_64KB
>  	def_bool y
> -	depends on !ARM64_64K_PAGES
>  	depends on !PAGE_SIZE_64KB
> -	depends on !PARISC_PAGE_SIZE_64KB
>  	depends on PAGE_SIZE_LESS_THAN_256KB
>  
>  config PAGE_SIZE_LESS_THAN_256KB
>  	def_bool y
>  	depends on !PAGE_SIZE_256KB
>  
> +config PAGE_SHIFT
> +	int
> +	default 12 if PAGE_SIZE_4KB
> +	default 13 if PAGE_SIZE_8KB
> +	default 14 if PAGE_SIZE_16KB
> +	default 15 if PAGE_SIZE_32KB
> +	default 16 if PAGE_SIZE_64KB
> +	default 18 if PAGE_SIZE_256KB
> +
>  # This allows to use a set of generic functions to determine mmap base
>  # address by giving priority to top-down scheme only if the process
>  # is not in legacy mode (compat task, unlimited stack size or
> diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
> index a880ee067d2e..aac46ee1a000 100644
> --- a/arch/hexagon/Kconfig
> +++ b/arch/hexagon/Kconfig
> @@ -8,6 +8,11 @@ config HEXAGON
>  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
>  	select ARCH_NO_PREEMPT
>  	select DMA_GLOBAL_POOL
> +	select FRAME_POINTER

Looks like a paste error.

> +	select HAVE_PAGE_SIZE_4KB
> +	select HAVE_PAGE_SIZE_16KB
> +	select HAVE_PAGE_SIZE_64KB
> +	select HAVE_PAGE_SIZE_256KB
>  	# Other pending projects/to-do items.
>  	# select HAVE_REGS_AND_STACK_ACCESS_API
>  	# select HAVE_HW_BREAKPOINT if PERF_EVENTS
> @@ -120,26 +125,6 @@ config NR_CPUS
>  	  This is purely to save memory - each supported CPU adds
>  	  approximately eight kilobytes to the kernel image.
>  
> -choice
> -	prompt "Kernel page size"
> -	default PAGE_SIZE_4KB
> -	help
> -	  Changes the default page size; use with caution.
> -
> -config PAGE_SIZE_4KB
> -	bool "4KB"
> -
> -config PAGE_SIZE_16KB
> -	bool "16KB"
> -
> -config PAGE_SIZE_64KB
> -	bool "64KB"
> -
> -config PAGE_SIZE_256KB
> -	bool "256KB"
> -
> -endchoice
> -
>  source "kernel/Kconfig.hz"
>  
>  endmenu
> diff --git a/arch/hexagon/include/asm/page.h b/arch/hexagon/include/asm/page.h
> index 10f1bc07423c..65c9bac639fa 100644
> --- a/arch/hexagon/include/asm/page.h
> +++ b/arch/hexagon/include/asm/page.h
> @@ -13,27 +13,22 @@
>  /*  This is probably not the most graceful way to handle this.  */
>  
>  #ifdef CONFIG_PAGE_SIZE_4KB
> -#define PAGE_SHIFT 12
>  #define HEXAGON_L1_PTE_SIZE __HVM_PDE_S_4KB
>  #endif
>  
>  #ifdef CONFIG_PAGE_SIZE_16KB
> -#define PAGE_SHIFT 14
>  #define HEXAGON_L1_PTE_SIZE __HVM_PDE_S_16KB
>  #endif
>  
>  #ifdef CONFIG_PAGE_SIZE_64KB
> -#define PAGE_SHIFT 16
>  #define HEXAGON_L1_PTE_SIZE __HVM_PDE_S_64KB
>  #endif
>  
>  #ifdef CONFIG_PAGE_SIZE_256KB
> -#define PAGE_SHIFT 18
>  #define HEXAGON_L1_PTE_SIZE __HVM_PDE_S_256KB
>  #endif
>  
>  #ifdef CONFIG_PAGE_SIZE_1MB
> -#define PAGE_SHIFT 20
>  #define HEXAGON_L1_PTE_SIZE __HVM_PDE_S_1MB
>  #endif

The corresponding Kconfig option does not exist (and did not exist before this
patch).

>  
> @@ -50,6 +45,7 @@
>  #define HVM_HUGEPAGE_SIZE 0x5
>  #endif
>  
> +#define PAGE_SHIFT CONFIG_PAGE_SHIFT
>  #define PAGE_SIZE  (1UL << PAGE_SHIFT)
>  #define PAGE_MASK  (~((1 << PAGE_SHIFT) - 1))
>