I have found an environmental difference between the two servers, one of which runs linux-image-2.6.26-2-s390x (and will boot) and the other of which runs linux-image-2.6.26-2-s390 (and will not boot). The s390x server has only one virtual CPU. The s390 server has two virtual CPUs. I changed the s390 version to have only one virtual CPU and tried again. This time it fails in a different way. With two virtual CPUs I get a kernel panic and the virtual machine loads a disabled wait PSW. With one virtual CPU the kernel goes into an infinite loop. The last message written to the console prior to the loop is
NET: Registered protocol family 17 During the infinite loop the kernel produces no messages. The loop was detected by monitoring software on z/VM. Of course it should work with 1 or 2 virtual CPUs, since the kernel has SMP support. But it doesn't work with either. It does fail differently, however, between the two scenarios. linux-image-2.6.26-1-s390 continues to work fine. The s390 server has "MACH XA" in its CP directory entry. The s390x server has "MACH ESA" in its CP directory entry. If I change the s390 server to use "MACH ESA", like the s390x server, it goes back to the original mode of failure (kernel panic, disabled wait) even with only one virtual CPU.
