[PATCH 04/11 v2] [POWERPC] Remove and replace uses of PPC_MEMSTART with memstart_addr

[Kumar Gala]

On Apr 1, 2008, at 5:50 AM, Paul Mackerras wrote:
> Kumar Gala writes:
>
>> For the sub-arches that support relocatable interrupt vectors (book- 
>> e) its
>> reasonable to have memory start at a non-zero physical address.   
>> For those
>> cases use the variable memstart_addr instead of the #define  
>> PPC_MEMSTART
>> since the only uses of PPC_MEMSTART are for initialization and in the
>> future we can set memstart_addr at runtime to have a relocatable  
>> kernel.
>
> In those cases, is it still true that the kernel sits at the start of
> the usable memory, or might there be usable memory before _stext?
> In other words, is PAGE_OFFSET == KERNELBASE still true or not?

Both cases are possible.

Here are the four cases I see:
* Normal kernel (kernel at physical 0)
* kexec kernel (kernel at physical 32M, but still has access to memory  
from physical 0 to 32M)

* cAMP kernel (kernel at non-zero offset) [eg. 256M offset]
* kexec cAMP kernel (kernel at 256M+32M, but has access to 256M + size)

- k