[PATCH] makedumpfile: s390x: Fix KVBASE to correct value for s390x arcitecture.

[Michael Holzheu]

Hello Ken'inchi,

On Thu, 2011-03-17 at 15:39 +0900, Ken'ichi Ohmichi wrote:
> Hi Mahesh,
> 
> On Tue, 15 Mar 2011 22:39:23 +0530
> Mahesh J Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> >
> > From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> > 
> > While excluding free pages from s390x dumps taken on LPAR, makedumpfile
> > fails to convert page address to pfn. The reason is, the memory for
> > mem_section structure is allocated below '_stext' and since KVBASE is
> > set to SYMBOL(_stext), the function is_kvaddr() fails and return NULL
> > address.
> 
> Why do we need this patch ?
> to support the latest kernel version of s390 ?
> or to support LPAR of s390 ?

The problem is that on s390 depending on the kernel configuration it can
happen that memory below _stext is available for buffer allocation.
Therefore the mem_section structure has been allocated below _stext. On
s390 the kernel page tables have a 1:1 mapping from 0 to memory_end
(memory holes are possible). Therefore I think the check "> 0" is ok for
s390.

> 
> I'd like to know whether we need a similar change for the other architecture.
> I will appreciate if getting a hint.

Not sure, if other architectures use memory below _stext for buffer
allocation.

Michael