Re: [PATCH V4 2/7] powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 11/04/2022 à 07:31, Anshuman Khandual a écrit :
> 
> 
> On 4/9/22 17:06, Christophe Leroy wrote:
>>
>>
>> Le 08/04/2022 à 14:53, Christophe Leroy a écrit :
>>>
>>>
>>> Le 07/04/2022 à 12:32, 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 powerpc_vm_get_page_prot() and moves it near
>>>> vm_get_page_prot().
>>>>
>>>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>>>> Cc: Paul Mackerras <paulus@samba.org>
>>>> Cc: linuxppc-dev@lists.ozlabs.org
>>>> Cc: linux-kernel@vger.kernel.org
>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>>>> ---
>>>>    arch/powerpc/Kconfig            |  1 +
>>>>    arch/powerpc/include/asm/mman.h | 12 ------------
>>>>    arch/powerpc/mm/mmap.c          | 26 ++++++++++++++++++++++++++
>>>>    3 files changed, 27 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>>> index 174edabb74fa..eb9b6ddbf92f 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
>>>>        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/mmap.c b/arch/powerpc/mm/mmap.c
>>>> index c475cf810aa8..cd17bd6fa36b 100644
>>>> --- a/arch/powerpc/mm/mmap.c
>>>> +++ b/arch/powerpc/mm/mmap.c
>>>> @@ -254,3 +254,29 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
>>>>            mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>>>>        }
>>>>    }
>>>> +
>>>> +#ifdef CONFIG_PPC64
>>>> +static pgprot_t powerpc_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
>>>> +}
>>>> +#else
>>>> +static pgprot_t powerpc_vm_get_page_prot(unsigned long vm_flags)
>>>> +{
>>>> +    return __pgprot(0);
>>>> +}
>>>> +#endif /* CONFIG_PPC64 */
>>>
>>> Can we reduce this forest of #ifdefs and make it more readable ?
>>>
>>> mm/mmap.c is going away with patch https://patchwork.ozlabs.org/project/linuxppc-dev/patch/d6d849621f821af253e777a24eda4c648814a76e.1646847562.git.christophe.leroy@csgroup.eu/
>>>
>>> So it would be better to add two versions of vm_get_page_prot(), for instance one in mm/pgtable_64.c and one in mm/pgtable_32.c
>>
>> Indeed, you don't need anything at all for PPC32. All you need to do is
>>
>>      select ARCH_HAS_VM_GET_PAGE_PROT if PPC64
>>
>> And in fact it could even be PPC_BOOK3S_64 instead of PPC64 because CONFIG_PPC_MEM_KEYS depends on PPC_BOOK3S_64 and _PAGE_SAO is 0 on nohash/64.
>>
>> So you can then put it into arch/powerpc/mm/book3s64/pgtable.c
> 
> Would something like the following change work ?

Yes that looks good to me.

Thanks
Christophe

> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index eb9b6ddbf92f..69e44358a235 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -140,7 +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
> +       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/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
> index 052e6590f84f..59d235519b44 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);