linux-kernel - Re: [v3][PATCH 7/8] book3e/kexec/kdump: redefine VIRT_PHYS

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Date:	Wed, 10 Jul 2013 13:46:00 +0800
From:	"tiejun.chen" <tiejun.chen@...driver.com>
To:	Bhushan Bharat-R65777 <R65777@...escale.com>
CC:	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [v3][PATCH 7/8] book3e/kexec/kdump: redefine VIRT_PHYS_OFFSET

On 07/10/2013 01:20 PM, Bhushan Bharat-R65777 wrote:
>
>
>> -----Original Message-----
>> From: Linuxppc-dev [mailto:linuxppc-dev-
>> bounces+bharat.bhushan=freescale.com@...ts.ozlabs.org] On Behalf Of Tiejun Chen
>> Sent: Tuesday, July 09, 2013 1:33 PM
>> To: benh@...nel.crashing.org
>> Cc: linuxppc-dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org
>> Subject: [v3][PATCH 7/8] book3e/kexec/kdump: redefine VIRT_PHYS_OFFSET
>>
>> Book3e is always aligned 1GB to create TLB so we should
>> use (KERNELBASE - MEMORY_START) as VIRT_PHYS_OFFSET to
>> get __pa/__va properly while boot kdump.
>>
>> Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
>> ---
>>   arch/powerpc/include/asm/page.h |    2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
>> index 988c812..5b00081 100644
>> --- a/arch/powerpc/include/asm/page.h
>> +++ b/arch/powerpc/include/asm/page.h
>> @@ -112,6 +112,8 @@ extern long long virt_phys_offset;
>>   /* See Description below for VIRT_PHYS_OFFSET */
>>   #ifdef CONFIG_RELOCATABLE_PPC32
>>   #define VIRT_PHYS_OFFSET virt_phys_offset
>> +#elif defined(CONFIG_PPC_BOOK3E_64)
>> +#define VIRT_PHYS_OFFSET (KERNELBASE - MEMORY_START)
>
> Can you please explain this code a bit more. I am not understanding this part:)

Nothing is special, we only need to redefine this to make sure __va()/__pa() can 
work well for BOOk3E-64 in BOOKE case:

#ifdef CONFIG_BOOKE
#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) + VIRT_PHYS_OFFSET))
#define __pa(x) ((unsigned long)(x) - VIRT_PHYS_OFFSET)

And the arch/powerpc/include/asm/page.h file has more descriptions inline :)

Tiejun
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