Re: [PATCH v4] [x86] detect and report lack of NX protections

[H. Peter Anvin]

The more I stare at the underlying code, the more I'm convinced that the
fundamental problem is that the underlying code is insane, with multiple
levels of detection for what amounts to cpu_has_nx, each effectively
checking what the previous code has done.

check_efer(), for example, screws with EFER, but EFER is simply set in
head_64.S from CPUID (unless Xen does something insane -- but if so, Xen
should clear X86_FEATURE_NX instead.)

The 32-bit startup code also sets NX, but yet on 32 bits we wiggle EFER
as if it had never been.  This code is screaming for cleanup and
unification.

	-hpa

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