Re: BUG: unable to handle kernel paging request - balloon_init - xen-4.1.0 - 2.6.32.39

[Scott Garron <xen-devel@sce.pridelands.org>]

Scott Garron wrote:
> Just for kicks, I tried hexediting balloon.o and changing that
> instruction to "imul   $0x1,%rdx,%rcx" (since multiplying by 1 will
> essentially nullify the instruction), but the end result was still
> the same crash, even though the value for "page" ended up being
> 0x0000000000100000.

      While still thinking along those lines, I re-enabled
CONFIG_SPARSEMEM_VMEMMAP, then hexedited the instruction again, and the
kernel got further along in the boot process, but crashed while trying
to free the initrd memory.

The serial console from that boot is at:

http://www.pridelands.org/~simba/xen-debug/hailstorm-fullserial20110428-afterhexedit.txt

      My deduction so far is that "page = pfn_to_page(pfn);" is somehow
returning a location that isn't quite "correct", but removing the
"multipliply by 0x38" instruction only returned something partially
usable and it took a dump all over the memory pages.

      Admittedly, I really know little about how all of this works, so my
debugging process is like taking stabs in the dark.  It's somewhat
intriguing to me, so I'm pretty much just playing with it until someone
who knows more can reproduce it.  It's hard to imagine that I'm the only
one having this problem with the current "xen/stable-2.6.32.x" branch.

-- 
Scott Garron