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

[Anshuman Khandual]

On 4/12/22 17:57, Christophe Leroy wrote:
> 
> 
> 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);
> }

Okay, will integrate these functions into vm_get_page_prot() as suggested.