RE: [v3][PATCH 7/8] book3e/kexec/kdump: redefine VIRT_PHYS_OFFSET

[Bhushan Bharat-R65777]

> -----Original Message-----
> From: Linuxppc-dev [mailto:linuxppc-dev-
> bounces+bharat.bhushan=freescale.com@xxxxxxxxxxxxxxxx] On Behalf Of Tiejun Chen
> Sent: Tuesday, July 09, 2013 1:33 PM
> To: benh@xxxxxxxxxxxxxxxxxxx
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> 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@xxxxxxxxxxxxx>
> ---
>  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:)

-Bharat

>  #else
>  #define VIRT_PHYS_OFFSET (KERNELBASE - PHYSICAL_START)
>  #endif
> --
> 1.7.9.5
> 
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