From: Ingo Molnar <mingo@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: "Zhang, Rui" <rui.zhang@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-perf-users@vger.kernel.org"
<linux-perf-users@vger.kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"kan.liang@linux.intel.com" <kan.liang@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake
Date: Fri, 6 Jan 2023 12:33:05 +0100 [thread overview]
Message-ID: <Y7gG8R8ZRWTXYSGq@gmail.com> (raw)
In-Reply-To: <Y7gB+uVpSJAQ6p+9@zn.tnic>
* 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
next prev parent reply other threads:[~2023-01-06 11:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-04 14:58 [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake Zhang Rui
2023-01-04 14:58 ` [PATCH 2/2] perf/x86/rapl: Add support for Intel Emerald Rapids Zhang Rui
2023-01-04 20:08 ` [tip: perf/urgent] " tip-bot2 for Zhang Rui
2023-01-04 16:55 ` [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake Dave Hansen
2023-01-05 6:54 ` Zhang, Rui
2023-01-05 9:55 ` Borislav Petkov
2023-01-06 6:05 ` Zhang, Rui
2023-01-06 10:14 ` Ingo Molnar
2023-01-06 10:39 ` Borislav Petkov
2023-01-06 10:56 ` Ingo Molnar
2023-01-06 11:11 ` Borislav Petkov
2023-01-06 11:33 ` Ingo Molnar [this message]
2023-01-06 14:45 ` Zhang, Rui
2023-01-06 14:38 ` Zhang, Rui
2023-01-06 14:49 ` Borislav Petkov
2023-01-06 14:50 ` Dave Hansen
2023-01-07 14:07 ` Zhang, Rui
2023-01-04 20:08 ` [tip: perf/urgent] " tip-bot2 for Zhang Rui
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