> could you explain this a little further. pae would normally > not be useful with 2gb of ram and is often of dubious utility > on a 4gb machine. what's different about xen?
PAE is of no utility at all as far as I can see, but sometimes we have to run xen guests on somebody else's hypervisor (think virtual hosting companies). If the hypervisor is configured with PAE (or 64-bit, it seems), the guest has to run in PAE mode. I hacked the Plan 9 xen kernel to support PAE for this reason, but since my xen test machine has only a couple of gigs I have never actually seen it work in the non-trivial case where the upper half of a 64-bit page address is non-zero. If our friend has more than 4GB and the panic disappears when he uses less than 2GB, that might indicate why he's having problems that nobody else has seen.
