CONFIG_ALPHA_QEMU is not available for thedefaultarchitecture x86.
Result is shown for architecture alpha

Run under QEMU emulation

configname: CONFIG_ALPHA_QEMU

Linux Kernel Configuration
└─>System setup
└─>Run under QEMU emulation
In linux kernel since version 3.13 (release Date: 2014-01-19)  
Assume the presence of special features supported by QEMU PALcode
that reduce the overhead of system emulation.

Generic kernels will auto-detect QEMU. But when building a
system-specific kernel, the assumption is that we want to
eliminate as many runtime tests as possible.

If unsure, say N.

depends
NOT CONFIG_ALPHA_GENERIC