linux-kernel - Re: [PATCH v2 2/9] mm: move __phys_to_pfn and __pfn_to_phys to asm/generic/memory

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Message-ID: <CANMBJr7Su2Gw_4oUj11grO-GMP-+tP0yp52zYB8KA3s5vo76VA@mail.gmail.com>
Date:	Tue, 29 Sep 2015 12:36:36 -0700
From:	Tyler Baker <tyler.baker@...aro.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	Russell King <linux@....linux.org.uk>,
	linux-nvdimm@...ts.01.org, Boaz Harrosh <boaz@...xistor.com>,
	david <david@...morbit.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>, Linux MM <linux-mm@...ck.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 2/9] mm: move __phys_to_pfn and __pfn_to_phys to asm/generic/memory_model.h

On 29 September 2015 at 12:21, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> On Tue, 25 Aug 2015, Dan Williams wrote:
>
>> From: Christoph Hellwig <hch@....de>
>>
>> Three architectures already define these, and we'll need them genericly
>> soon.
>>
>> Signed-off-by: Christoph Hellwig <hch@....de>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>> ---
>>  arch/arm/include/asm/memory.h       |    6 ------
>>  arch/arm64/include/asm/memory.h     |    6 ------
>>  arch/unicore32/include/asm/memory.h |    6 ------
>>  include/asm-generic/memory_model.h  |    6 ++++++
>>  4 files changed, 6 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>> index b7f6fb462ea0..98d58bb04ac5 100644
>> --- a/arch/arm/include/asm/memory.h
>> +++ b/arch/arm/include/asm/memory.h
>> @@ -119,12 +119,6 @@
>>  #endif
>>
>>  /*
>> - * Convert a physical address to a Page Frame Number and back
>> - */
>> -#define      __phys_to_pfn(paddr)    ((unsigned long)((paddr) >> PAGE_SHIFT))
>> -#define      __pfn_to_phys(pfn)      ((phys_addr_t)(pfn) << PAGE_SHIFT)
>> -
>> -/*
>>   * Convert a page to/from a physical address
>>   */
>>  #define page_to_phys(page)   (__pfn_to_phys(page_to_pfn(page)))
>
> [...]
>
>> diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
>> index 14909b0b9cae..f20f407ce45d 100644
>> --- a/include/asm-generic/memory_model.h
>> +++ b/include/asm-generic/memory_model.h
>> @@ -69,6 +69,12 @@
>>  })
>>  #endif /* CONFIG_FLATMEM/DISCONTIGMEM/SPARSEMEM */
>>
>> +/*
>> + * Convert a physical address to a Page Frame Number and back
>> + */
>> +#define      __phys_to_pfn(paddr)    ((unsigned long)((paddr) >> PAGE_SHIFT))
>> +#define      __pfn_to_phys(pfn)      ((pfn) << PAGE_SHIFT)
>> +
>
> This patch, currently in mainline as commit 012dcef3f0, breaks LPAE on
> ARM32 with more than 4GB of RAM. The phys_addr_t cast in the original
> ARM definition is important when LPAE is enabled as phys_addr_t is 64
> bits while longs are 32 bits.

Dan sent my fix above to Linus already, which is in mainline as commit
ae4f97696889.

Cheers,

Tyler
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