The following applies to latest "Development stream", currently based on kernel 3.12.
IBM support is available for
for Linux on System z® running:
IBM System z (or System z, for short) is used on these pages when referring to the above mentioned mainframes.
Starting with the kernel 2.6.27 based "Development stream", IBM supports only distributions compiled with march=z9-109, so that Linux on System z can benefit from the compiler enhancements exploiting z9 instructions.
IBM supports only 64-bit distributions based on this stream; 31-bit applications are supported on the 31-bit emulation layer.