As announced in July 2011 , the openSUSE Xen maintainers intended to discontinue support for 32-bit Xen host in openSUSE12.1. Now that 12.1 has been released, we are hearing complaints from users virtualizing on older P4-based systems. I understand their frustration, but given that the upstream Xen community has ignored the 32-bit host, and no other distros are supporting it, we can no longer justify the effort required to support it. Supported 32-bit Xen packages are going by way of the dodo, and dropping them in openSUSE may very well mean extinction.
That said, users still have a few options. First, we have quite stable 32 and 64-bit Xen packages in openSUSE11.4. The Xen version is 4.0.3, which has all the latest upstream fixes and improvements for the 4.0 branch. In fact, the package sources are shared with SLES11 SP1 and benefit from the broader user-base and QA of the enterprise product. openSUSE11.4 contains kernel version 2.6.37, which has excellent support for older P4-based hardware.
Another option is using the openSUSE Build Service to maintain your own 32-bit Xen packages. In fact, the community itself can maintain 32-bit Xen in the Virtualization project if there is enough interest. We will be happy to accept any patches that do not break 64-bit environments :-). One benefit of this option is that the openSUSE Factory Xen packages are developed in the Virtualization project. A community maintained, 32-bit Xen host in this project would be submitted to Factory, and hence included in the next openSUSE release, as part of the overall Xen package submission done by the openSUSE maintainers.