linux-kernel - [PATCH 0/7] x86/topology: Improve CPUID.1F handling

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Date:   Fri, 12 Aug 2022 23:08:38 +0800
From:   Zhang Rui <rui.zhang@...el.com>
To:     LKML <linux-kernel@...r.kernel.org>, x86@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, "H. Peter Anvin" <hpa@...or.com>,
        Len Brown <len.brown@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 0/7] x86/topology: Improve CPUID.1F handling

On Intel AlderLake-N platforms where there are Ecores only, the Ecore
Module topology is enumerated via CPUID.1F Module level, which has not
been supported by Linux kernel yet.

This exposes two issues in current CPUID.1F handling code.
1. Linux interprets the Module id bits as package id and erroneously
reports a multi module system as a multi-package system.
2. Linux excludes the unknown Module id bits from the core_id, and
results in duplicate core_id’s shown in a package after the first issue
solved.

Plus that, a third problem is observed on Intel Hybrid ADL-S/P
platforms. The return value of CPUID.1F SMT level EBX (number of
siblings) differs on Pcore CPUs and Ecore CPUs, and results in
inconsistent smp_num_siblings value based on the Pcore/Ecore CPU
enumeration order.

Patch 1/7 and 2/7 fix the first two issues. And at the same time, it
reveals a reality that the core_id could be sparse on platforms with
CPUID.1F support.
Patch 3/7 improves coretemp driver code to be able to handle sparse and
large core id, which is the only driver that uses core_id as array
index and run on platforms with CPUID.1F support.

Patch 4/7 to 7/7 propose a fix for the third problem and update the
related Documents.

The patch series have been tested on Intel ICL/CLX servers, SKL/KBL/ADL
clients.

thanks,
-rui