This patch seems to solve the primary issue. It is not yet, anywhere upstream as far as I know. So it may cause other side effects or get changed before it is finally submitted.
With this applied I was able to boot pre-3.0 kernels as HVM guests under Oneiric again. However booting an Oneiric guest triggers the same issues with a change enabling IPI events and Xen spinlocks. This time the 4.1.1 hypervisor is supposed to support them.
This patch seems to solve the primary issue. It is not yet, anywhere upstream as far as I know. So it may cause other side effects or get changed before it is finally submitted.
With this applied I was able to boot pre-3.0 kernels as HVM guests under Oneiric again. However booting an Oneiric guest triggers the same issues with a change enabling IPI events and Xen spinlocks. This time the 4.1.1 hypervisor is supposed to support them.