[PATCH 4/11] powerpc: Add CONFIG_CRASH_DUMP

[Haren Myneni]

Olaf Hering wrote:

> On Tue, Jan 03, Haren Myneni wrote:
>
>  
>
>>Yes, it could be a problem if we do OF boot at 32MB (CONFIG_CRASH_DUMP) 
>>since the the initrd's location is set at 36MB by the yaboot. However, 
>>in the kdump boot, the initrd location is not at fixed location and 
>>changed by the kexec-tool.
>>
>>But, we found an issue (Oops) when we load the second kernel in to the 
>>crash kernel region. During the first boot, the crash kernel region is 
>>reserved (32M - 160M for crashkernel=128M at 32M) and the initrd is at 36M. 
>>But, after loading the initrd, free_initrd() is freed initrd region even 
>>though it is part of crash kernel reserved region. When we load the 
>>second kernel using kexec-tool, we are copying into unallocated memory. 
>>Thus caused panic.
>>    
>>
>
>Why are all these values hardcoded? Cant this be probed at runtime
>somehow? I hope the only fixed address is the entry point of the inital
>bootloader (yaboot or zImage).
>I will finally change yaboot this week to not use hardcoded values
>anymore.
>
>
>  
>
I am not sure whether yaboot can find the initrd location at runtime. If 
the yaboot can probe and find the crashkernel end at run time, then we 
might be considering 2 issues:
- At present, alloc_bottom is moved after initrd_end. But it has to be 
before rmo_top. Hence, need changes in prom_init.c. we also need to make 
sure that sufficient memory is available before rmo_top for RTAS and 
reserve map. Otherwise prom_claim() will get failed. Right?
- As you pointed out before (minor one), the existing yaboot will not 
work with the new kernel. Ex: SLES9's yaboot for SLES10 kernel.