x86 pause misbehaves with -cpu haswell

Using qemu-2.9.0

When booting NetBSD using '-cpu haswell -smp 4', the system fails to initialize the additional CPUs.  It appears as though the "application processor" enters routine x86_pause() but never returns.  

x86_pause() is simply two assembler instructions: 'pause; ret;'

Replacing the routine with 'nop; nop; ret;' allows the system to proceed, of course without the benefit of the pause instruction on spin-loops!

Additionally, booting with '-cpu phenom -smp 4' also works, although the system does seem confused about the type of CPU being used.