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Date:   Tue, 03 Jun 2014 16:47:52 -0700
From:   David Daney <ddaney.cavm@gmail.com>
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To:     Ralf Baechle <ralf@linux-mips.org>
CC:     Huacai Chen <chenhc@lemote.com>, John Crispin <john@phrozen.org>,
        "Steven J. Hill" <Steven.Hill@imgtec.com>,
        Aurelien Jarno <aurelien@aurel32.net>,
        linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>,
        Zhangjin Wu <wuzhangjin@gmail.com>
Subject: Re: [PATCH V2 4/8] MIPS: Add NUMA support for Loongson-3
References: <1397348662-22502-1-git-send-email-chenhc@lemote.com> <1397348662-22502-5-git-send-email-chenhc@lemote.com> <20140603224739.GU17197@linux-mips.org>
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On 06/03/2014 03:47 PM, Ralf Baechle wrote:
[...]
>> --- a/arch/mips/include/asm/addrspace.h
>> +++ b/arch/mips/include/asm/addrspace.h
>> @@ -51,8 +51,14 @@
>>    * Returns the physical address of a CKSEGx / XKPHYS address
>>    */
>>   #define CPHYSADDR(a)		((_ACAST32_(a)) & 0x1fffffff)
>> +
>> +#ifndef CONFIG_NUMA
>>   #define XPHYSADDR(a)		((_ACAST64_(a)) &			\
>>   				 _CONST64_(0x000000ffffffffff))
>> +#else
>> +#define XPHYSADDR(a)		((_ACAST64_(a)) &			\
>> +				 _CONST64_(0x0000ffffffffffff))
>> +#endif
>
> The mask in XPHYSADDR is a function of the processor architecture, not
> imlementation, not NUMA.  The latest version of the MIPS architecture
> permits PABITS to be as large as 49 bits, so the mask should be
> 0x0001ffffffffffff.  Always.
>
>> diff --git a/arch/mips/include/asm/sparsemem.h b/arch/mips/include/asm/sparsemem.h
>> index d2da53c..c001a90 100644
>> --- a/arch/mips/include/asm/sparsemem.h
>> +++ b/arch/mips/include/asm/sparsemem.h
>> @@ -11,7 +11,12 @@
>>   #else
>>   # define SECTION_SIZE_BITS	28
>>   #endif
>> +
>> +#ifdef CONFIG_NUMA
>> +#define MAX_PHYSMEM_BITS	48
>> +#else
>>   #define MAX_PHYSMEM_BITS	35
>> +#endif
>
> Essentially the same comment as for XPHYSADDR above.

Are you saying to change it to 49 unconditionally for all configurations?

That would work for OCTEON too, where we have had to increase it to 42.

What are the implications for kernel data structures if this is set many 
orders of magnitude greater than the actual number of bits used on a system?


>
>    Ralf
>
>
>