linux-kernel - Re: [RFC PATCH 03/15] x86/cpu/intel: Fix init_intel() checks for extended family numbers

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Message-ID: <54df5b3f-8b98-42b8-b3ec-3860abd5ce67@intel.com>
Date: Fri, 20 Dec 2024 15:27:41 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Sohil Mehta <sohil.mehta@...el.com>, x86@...nel.org,
 Dave Hansen <dave.hansen@...ux.intel.com>, Tony Luck <tony.luck@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>,
 Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>,
 "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Andy Lutomirski <luto@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>,
 Fenghua Yu <fenghua.yu@...el.com>, Jean Delvare <jdelvare@...e.com>,
 Guenter Roeck <linux@...ck-us.net>, Zhang Rui <rui.zhang@...el.com>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-hwmon@...r.kernel.org
Subject: Re: [RFC PATCH 03/15] x86/cpu/intel: Fix init_intel() checks for
 extended family numbers

On 12/20/24 13:36, Sohil Mehta wrote:
> X86_FEATURE_REP_GOOD is only set for family 6 processors.  Extend the
> check to family numbers beyond 15.

Could you explain why, please?

> It is uncertain whether the Pentium 4s (family 15) should set the
> feature flag as well. Commit 185f3b9da24c ("x86: make intel.c have
> 64-bit support code") that originally set X86_FEATURE_REP_GOOD also set
> the x86_cache_alignment preference for family 15 processors. The
> omission of the family 15 seems intentional.
> 
> Also, the 32-bit user copy alignment preference is only set for family 6
> and 15 processors. Extend the preference to family numbers beyond 15.

Can you please provide some more context so it's clear which hunk this
refers to?  Alternatively, can you break this out into a separate patch?