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

[tiejun.chen]

On 07/10/2013 01:20 PM, Bhushan Bharat-R65777 wrote:
> > -----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:)

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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