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

[Matthew Garrett]

On Tue, Nov 17, 2020 at 1:21 PM Matthew Garrett <mjg59@xxxxxxxxxx> wrote:
>
> 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.

But ha ok based on Borislav's response it looks like someone's already
done that.