Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid

From: Borislav Petkov
Date: Tue Feb 05 2019 - 10:43:24 EST

On Tue, Feb 05, 2019 at 07:19:16AM -0800, Dave Hansen wrote:
> This is one of the few times that we're pretty confident that folks will
> use this. The reason we're going to this trouble is that the split lock
> detection is wanted by actual customers, and they want it before it's
> implemented on a processor with real enumeration.
> This isn't something we want everybody and their grandma to turn on;
> it's a rather specialized feature. It's really only for folks that care
> about the latency incurred across the entire system on split lock
> operations.


> It's not for developers. This really is for (somewhat niche) end users
> that want split lock detection in production. This is all really an
> effort to get them running mainline or real distro kernels.

This all sounds to me like it shouldn't even be mainline but in a
special, evaluation kernel. If anything, it should be default off and be
opted-in by a cmdline switch. None of that *cpuid=* toggling dance.


Good mailing practices for 400: avoid top-posting and trim the reply.