RE: [Xen-devel] Xen at scale

[MAGENHEIMER,DAN (HP-FtCollins,ex1) <dan...@hp...>]

>> My wish list based on my experience so far:
>>        HIGHMEM4G - This is my top wish, and I will work on it myself
>>             when I get a chance, though I can't say when that
>> will be.
>
>Agreed. It should just be a case of putting the CONFIG_HIGHMEM4G
>stuff back into the following files:
>
>./include/asm-xeno/fixmap.h
>./include/asm-xeno/highmem.h
>./include/asm-xeno/pgtable.h
>./include/asm-xeno/page.h
>./arch/xeno/config.in
>./arch/xeno/mm/init.c
>./arch/xeno/kernel/setup.c

Here's a patch that adds back the CONFIG_HIGHMEM stuff.  It works
fine with CONFIG_HIGHMEM off and with CONFIG_HIGHMEM on with
dom0_memory <= 512MB, but fails with dom0_memory == 1GB (1048576)
on my 2GB machine.

The failure condition is that DOM0 barely launches, then causes
Xen to die and the machine reboots (even with reboot disabled, so
it must be trashing something in Xen itself).  I haven't been able
to get any debugging output (even panics) to show up from dom0 at all...
perhaps this will be a good opportunity to try out Alex's pdb
stuff.  (Alex, is there any way to set a breakpoint very early
in xenolinux startup?)

Anyway, I thought I'd post it in case someone with more xenolinux
setup/init debugging experience can easily spot/fix the problem,
but I'll keep trying.  (Please email if you find/fix it, to put
me out of my misery ;-)

As it works for everything that works today, the patch could be rolled
into the mainline, possibly with a runtime check and nicer error
message added.

Dan Magenheimer
HP Labs Fort Collins

P.S. No changes appeared to be required in page.h or setup.c
and I changed defconfig instead of config.in.