Re: [PATCH v14 0/9] x86/arch_prctl Add ARCH_[GET|SET]_CPUID for controlling the CPUID instruction

From: Thomas Gleixner
Date: Fri Feb 10 2017 - 09:04:57 EST

On Wed, 8 Feb 2017, Kyle Huey wrote:

> rr (, 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 v13:
> All: rebased on top of tglx's __switch_to_xtra patches
> (

That doesn't help because that patchset is stale and it has unresolved
comments. I don't know when I have cycles to revisit it, but if you want to
have a try feel free to do so.