The most suspicious part from me is, vm_physseg allocation code I made. I've confirmed: #define VM_PHYSSEG_MAX 1 #define VM_PHYSSEG_STRAT VM_PSTRAT_BSEARCH /* XXX */ #define VM_NFREELIST 1 #define VM_FREELIST_DEFAULT 0 works on powerpc/ibm40x. I can help to bisect if you tell me the config.