Stephane’s thoughts corner…

Stephane Bailliez's thoughts on everything

I wanted to recycle my old Dell D810 laptop (Pentium M 2GHZ, 2GB RAM, 80GB HD) that was sitting there doing nothing and install Xen on it so that I could have a server for development purposes as well as a media center. For some odd reasons I decided to install the latest Ubuntu 9.10 on it (making sure that it was actually working fine on the laptop)…and have a go at Xen 3.4.2… little did I know how much time I would spend on it. It wasn’t obviously the best match in all aspects.

For the details, I tried to use a vanilla kernel 2.6.31.12. I based the install from Brandon Turner blog entry (keep in mind a few things need to be adapted depending on your system, ). After many failed attempts due to bad grub2 configuration, I managed to load the kernel…a bit.. it crashes with:

Cannot access memory beyond end of bootstrap direct-map area, Unknown interrupt.

A little bit of googling direct me to a post in the xen-users mailing list:

No, it’ll be a 32-bit-specific issue though. I would recommend just running a 64-bit build of Xen, if the CPU supports 64-bit mode. It’ll be something to do with GRUB2 dumping the dom0 kernel and initrd higher in memory than GRUB1, past the end of where 32-bit Xen is set up to be able to access. Probably not a hard fix, although I have no GRUB2 installation to test with.

Ok, so..off we go, I’m downgrading grub2 and revert back to grub-legacy.

After a bit of fiddling, I manage to boot again only to be greeted by another giant stacktrace following:

BUG: unable to handle kernel paging request at c07ab790.

Obviously I can spend weeks on this, debugging and nagging xen-users, but I think I have played enough with patches and alternatives to figure out that best thing to do is to avoid that combination of Ubuntu 9.10 + Xen 3.4.2 on a Pentium M machine. I’ll see what VirtualBox looks like on 9.10 and then decides whether or not to try with an older distrib if it does not do the job.