Messages in this thread | | | Date | Fri, 6 Jan 2023 12:33:05 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake |
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* Borislav Petkov <bp@alien8.de> wrote:
> On Fri, Jan 06, 2023 at 11:56:18AM +0100, Ingo Molnar wrote: > > It's a trade-off in any case: there's a point where quirk flags or even > > feature flags become harder to read and harder to maintain than cleanly > > separated per model driver functions. > > Yeah, no, singular: a synthetic feature *flag*: X86_FEATURE_RAPL. > > cpu/intel.c can set it and driver can test it. > > Everything else inside the driver. > > Until Intel can get their act together and actually do a CPUID bit like AMD. :-P > > But when you think about it, whether the model matching happens in the driver or > in cpu/intel.c doesn't matter a whole lot. > > All that matters is, they should finally give it a CPUID bit.
The other thing that matters here are the RAPL *incompatibilities* between model variants, which are significant AFAICS.
With a CPUID we get a kind of semi-compatible hardware interface with well defined semantics & expansion.
With 'non-architectural', per-model RAPL features we get very little of that...
Which is why it's a trade-off that is hard to judge in advance: maybe we can simplify the code via a synthethic CPUID[s], maybe it will just be another zoo of per-model feature flags...
Likely won't be able to tell for sure until we see patches.
Thanks,
Ingo
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