Re: [PATCH -v2.1] x86/msr: Filter MSR writes

[Matthew Garrett]

On Tue, Nov 17, 2020 at 1:00 PM Mathieu Chouquet-Stringer
<me@mathieu.digital> wrote:

> I'm late to the party but it seems allowing MSR_IA32_ENERGY_PERF_BIAS
> has the downside of flagging the kernel as tainted without telling you
> why if you use something like x86_energy_perf_policy (from
> tools/power/x86/x86_energy_perf_policy) which itself is used by tuned.

I initially pushed back against a kernel interface for
MSR_IA32_ENERGY_PERF_BIAS (cc: Len Brown, who tried mightily to
convince me I was wrong here) on the grounds that it was exporting an
implementation detail rather than providing a generic interface, and
that it was something that could be done via userland instead. I
thought we'd end up with more examples of similar functionality and
could tie it into something more reasonable - history has proven me
wrong on that. I think it's probably reasonable to dust off the driver
that Len submitted however many years ago and push that into the
kernel now.