[PATCH v15 0/9] x86/arch_prctl Add ARCH_[GET|SET]_CPUID for controlling the CPUID instruction

From: Kyle Huey
Date: Sat Mar 11 2017 - 14:47:44 EST

rr (http://rr-project.org/), a userspace record-and-replay reverse-
execution debugger, would like to trap and emulate the CPUID instruction.
This would allow us to a) mask away certain hardware features that rr does
not support (e.g. RDRAND) and b) enable trace portability across machines
by providing constant results.

Newer Intel CPUs (Ivy Bridge and later) can fault when CPUID is executed at
CPL > 0. Expose this capability to userspace as a new pair of arch_prctls,

Since v14:
All: rebased onto x86/process, which contains the switch_to_xtra

Patch 4: x86/syscalls/32: Wire up arch_prctl on x86-32
- the new arch_prctl is now syscall number 384, because that was

Patch 5: x86/cpufeature: Detect CPUID faulting support
- the newly added probe_xeon_phi_r3mwait is called from