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Subject: Re: [PATCH 25/30] nios2/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
To:     Dinh Nguyen <dinguyen@kernel.org>, linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-arch@vger.kernel.org
References: <1644805853-21338-1-git-send-email-anshuman.khandual@arm.com>
 <1644805853-21338-26-git-send-email-anshuman.khandual@arm.com>
 <50ac6dc2-7c71-2a8b-aa00-78926351b252@kernel.org>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <637cfc45-60ad-3cd1-5127-76ecabb87def@arm.com>
Date:   Fri, 25 Feb 2022 14:22:03 +0530
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On 2/25/22 7:01 AM, Dinh Nguyen wrote:
> Hi Anshuman,
> 
> On 2/13/22 20:30, Anshuman Khandual wrote:
>> This defines and exports a platform specific custom vm_get_page_prot() via
>> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
>> macros can be dropped which are no longer needed.
>>
>> Cc: Dinh Nguyen <dinguyen@kernel.org>
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> Acked-by: Dinh Nguyen <dinguyen@kernel.org>
>> ---
>>   arch/nios2/Kconfig               |  1 +
>>   arch/nios2/include/asm/pgtable.h | 16 ------------
>>   arch/nios2/mm/init.c             | 45 ++++++++++++++++++++++++++++++++
>>   3 files changed, 46 insertions(+), 16 deletions(-)
>>
>> diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
>> index 33fd06f5fa41..85a58a357a3b 100644
>> --- a/arch/nios2/Kconfig
>> +++ b/arch/nios2/Kconfig
>> @@ -6,6 +6,7 @@ config NIOS2
>>       select ARCH_HAS_SYNC_DMA_FOR_CPU
>>       select ARCH_HAS_SYNC_DMA_FOR_DEVICE
>>       select ARCH_HAS_DMA_SET_UNCACHED
>> +    select ARCH_HAS_VM_GET_PAGE_PROT
>>       select ARCH_NO_SWAP
>>       select COMMON_CLK
>>       select TIMER_OF
>> diff --git a/arch/nios2/include/asm/pgtable.h b/arch/nios2/include/asm/pgtable.h
>> index 4a995fa628ee..2678dad58a63 100644
>> --- a/arch/nios2/include/asm/pgtable.h
>> +++ b/arch/nios2/include/asm/pgtable.h
>> @@ -40,24 +40,8 @@ struct mm_struct;
>>    */
>>     /* Remove W bit on private pages for COW support */
>> -#define __P000    MKP(0, 0, 0)
>> -#define __P001    MKP(0, 0, 1)
>> -#define __P010    MKP(0, 0, 0)    /* COW */
>> -#define __P011    MKP(0, 0, 1)    /* COW */
>> -#define __P100    MKP(1, 0, 0)
>> -#define __P101    MKP(1, 0, 1)
>> -#define __P110    MKP(1, 0, 0)    /* COW */
>> -#define __P111    MKP(1, 0, 1)    /* COW */
>>     /* Shared pages can have exact HW mapping */
>> -#define __S000    MKP(0, 0, 0)
>> -#define __S001    MKP(0, 0, 1)
>> -#define __S010    MKP(0, 1, 0)
>> -#define __S011    MKP(0, 1, 1)
>> -#define __S100    MKP(1, 0, 0)
>> -#define __S101    MKP(1, 0, 1)
>> -#define __S110    MKP(1, 1, 0)
>> -#define __S111    MKP(1, 1, 1)
>>     /* Used all over the kernel */
>>   #define PAGE_KERNEL __pgprot(_PAGE_PRESENT | _PAGE_CACHED | _PAGE_READ | \
>> diff --git a/arch/nios2/mm/init.c b/arch/nios2/mm/init.c
>> index 613fcaa5988a..311b2146a248 100644
>> --- a/arch/nios2/mm/init.c
>> +++ b/arch/nios2/mm/init.c
>> @@ -124,3 +124,48 @@ const char *arch_vma_name(struct vm_area_struct *vma)
>>   {
>>       return (vma->vm_start == KUSER_BASE) ? "[kuser]" : NULL;
>>   }
>> +
>> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
>> +{
>> +    switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
>> +    case VM_NONE:
>> +        return MKP(0, 0, 0);
>> +    case VM_READ:
>> +        return MKP(0, 0, 1);
>> +    /* COW */
>> +    case VM_WRITE:
>> +        return MKP(0, 0, 0);
>> +    /* COW */
>> +    case VM_WRITE | VM_READ:
>> +        return MKP(0, 0, 1);
>> +    case VM_EXEC:
>> +        return MKP(1, 0, 0);
>> +    case VM_EXEC | VM_READ:
>> +        return MKP(1, 0, 1);
>> +    /* COW */
>> +    case VM_EXEC | VM_WRITE:
>> +        return MKP(1, 0, 0);
>> +    /* COW */
>> +    case VM_EXEC | VM_WRITE | VM_READ:
>> +        return MKP(1, 0, 1);
>> +    case VM_SHARED:
>> +        return MKP(0, 0, 0);
>> +    case VM_SHARED | VM_READ:
>> +        return MKP(0, 0, 1);
>> +    case VM_SHARED | VM_WRITE:
>> +        return MKP(0, 1, 0);
>> +    case VM_SHARED | VM_WRITE | VM_READ:
>> +        return MKP(0, 1, 1);
>> +    case VM_SHARED | VM_EXEC:
>> +        return MKP(1, 0, 0);
>> +    case VM_SHARED | VM_EXEC | VM_READ:
>> +        return MKP(1, 0, 1);
>> +    case VM_SHARED | VM_EXEC | VM_WRITE:
>> +        return MKP(1, 1, 0);
>> +    case VM_SHARED | VM_EXEC | VM_WRITE | VM_READ:
>> +        return MKP(1, 1, 1);
>> +    default:
>> +        BUILD_BUG();
>> +    }
>> +}
>> +EXPORT_SYMBOL(vm_get_page_prot);
> 
> I'm getting this compile error after applying this patch when build NIOS2:

Hmm, that is strange.

Did you apply the entire series or atleast upto the nios2 patch ? Generic
vm_get_page_prot() should not be called (which is build complaining here)
when ARCH_HAS_VM_GET_PAGE_PROT is already enabled on nios2 platform.

Ran a quick build test on nios2 for the entire series and also just upto
this particular patch, build was successful.

> 
> 
> mm/mmap.c:105:2: error: ‘__P000’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |  ^~~~~~
> 
> mm/mmap.c:105:10: error: ‘__P001’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |          ^~~~~~
> 
> mm/mmap.c:105:18: error: ‘__P010’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                  ^~~~~~
> 
>   AR      fs/devpts/built-in.a
> 
> mm/mmap.c:105:26: error: ‘__P011’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                          ^~~~~~
> 
> mm/mmap.c:105:34: error: ‘__P100’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                                  ^~~~~~
> 
> mm/mmap.c:105:42: error: ‘__P101’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                                          ^~~~~~
> 
> mm/mmap.c:105:50: error: ‘__P110’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                                                  ^~~~~~
> 
> mm/mmap.c:105:58: error: ‘__P111’ undeclared here (not in a function)
> 
>   105 |  __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> 
>       |                                                          ^~~~~~
> 
> mm/mmap.c:106:2: error: ‘__S000’ undeclared here (not in a function)
> 
>   106 |  __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
> 
>       |  ^~~~~~
> 
> mm/mmap.c:106:10: error: ‘__S001’ undeclared here (not in a function)
> 
>   106 |  __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
> 
> 
> 
> Dinh
>