Re: [PATCH V5 2/7] powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Christophe Leroy]

Le 12/04/2022 à 06:38, Anshuman Khandual a écrit :
> This defines and exports a platform specific custom vm_get_page_prot() via
> subscribing ARCH_HAS_VM_GET_PAGE_PROT. While here, this also localizes
> arch_vm_get_page_prot() as __vm_get_page_prot() and moves it near
> vm_get_page_prot().
> 
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>   arch/powerpc/Kconfig               |  1 +
>   arch/powerpc/include/asm/mman.h    | 12 ------------
>   arch/powerpc/mm/book3s64/pgtable.c | 20 ++++++++++++++++++++
>   3 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 174edabb74fa..69e44358a235 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -140,6 +140,7 @@ config PPC
>   	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UACCESS_FLUSHCACHE
>   	select ARCH_HAS_UBSAN_SANITIZE_ALL
> +	select ARCH_HAS_VM_GET_PAGE_PROT	if PPC_BOOK3S_64
>   	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>   	select ARCH_KEEP_MEMBLOCK
>   	select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
> index 7cb6d18f5cd6..1b024e64c8ec 100644
> --- a/arch/powerpc/include/asm/mman.h
> +++ b/arch/powerpc/include/asm/mman.h
> @@ -24,18 +24,6 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
>   }
>   #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
>   
> -static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
> -{
> -#ifdef CONFIG_PPC_MEM_KEYS
> -	return (vm_flags & VM_SAO) ?
> -		__pgprot(_PAGE_SAO | vmflag_to_pte_pkey_bits(vm_flags)) :
> -		__pgprot(0 | vmflag_to_pte_pkey_bits(vm_flags));
> -#else
> -	return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : __pgprot(0);
> -#endif
> -}
> -#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags)
> -
>   static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
>   {
>   	if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
> diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
> index 052e6590f84f..d0319524e27f 100644
> --- a/arch/powerpc/mm/book3s64/pgtable.c
> +++ b/arch/powerpc/mm/book3s64/pgtable.c
> @@ -7,6 +7,7 @@
>   #include <linux/mm_types.h>
>   #include <linux/memblock.h>
>   #include <linux/memremap.h>
> +#include <linux/pkeys.h>
>   #include <linux/debugfs.h>
>   #include <misc/cxl-base.h>
>   
> @@ -549,3 +550,22 @@ unsigned long memremap_compat_align(void)
>   }
>   EXPORT_SYMBOL_GPL(memremap_compat_align);
>   #endif
> +
> +static pgprot_t __vm_get_page_prot(unsigned long vm_flags)
> +{
> +#ifdef CONFIG_PPC_MEM_KEYS
> +	return (vm_flags & VM_SAO) ?
> +		__pgprot(_PAGE_SAO | vmflag_to_pte_pkey_bits(vm_flags)) :
> +		__pgprot(0 | vmflag_to_pte_pkey_bits(vm_flags));
> +#else
> +	return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : __pgprot(0);
> +#endif
> +}
> +
> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
> +{
> +	return __pgprot(pgprot_val(protection_map[vm_flags &
> +			(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
> +			pgprot_val(__vm_get_page_prot(vm_flags)));
> +}
> +EXPORT_SYMBOL(vm_get_page_prot);

This looks functionnaly OK, but I think we could go in the same 
direction as ARM and try to integrate __vm_get_page_prot() inside 
vm_get_page_prot() to get something simpler and cleaner:

Something like below (untested):

pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
	unsigned long prot = pgprot_val(protection_map[vm_flags &
				 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);

	if (vm_flags & VM_SAO)
		prot |= _PAGE_SAO

#ifdef CONFIG_PPC_MEM_KEYS
	prot |= vmflag_to_pte_pkey_bits(vm_flags);
#endif

	return __pgprot(prot);
}