Messages in this thread | | | Date | Tue, 17 Nov 2020 22:20:16 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH -v2.1] x86/msr: Filter MSR writes |
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On Tue, Nov 17, 2020 at 10:00:18PM +0100, Mathieu Chouquet-Stringer 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.
Not for long:
https://git.kernel.org/tip/fe0a5788624c8b8f113a35bbe4636e37f9321241
> So while both documentation and tools should be updated as to be clearer > and to not taint the kernel respectively, there's something that remains > to be done to explain why or how the kernel got tainted because of > poking into MSRs...
Because if you poke at random MSRs and you manage to "configure" your CPU to run "out of spec" - this is what the taint flag is called: TAINT_CPU_OUT_OF_SPEC - then this is exactly the case you've created: a CPU executing outside of specifications.
I agree with the update-the-documentation aspect - S does not mean only SMP kernel on !SMP-capable CPU but the more general, CPU is out of spec.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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