linux-kernel - [tip:x86/urgent] x86/topology: Use total_cpus not nr_cpu

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Date:	Sat, 19 Mar 2016 02:31:29 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	bp@...en8.de, hpa@...or.com, umgwanakikbuti@...il.com,
	mingo@...nel.org, tglx@...utronix.de, aherrmann@...e.com,
	jencce.kernel@...il.com, linux-kernel@...r.kernel.org
Subject: [tip:x86/urgent] x86/topology: Use total_cpus not nr_cpu_ids for
 logical packages

Commit-ID:  3e8db2246b434c6b18a6a9f09904038bddcf76c7
Gitweb:     http://git.kernel.org/tip/3e8db2246b434c6b18a6a9f09904038bddcf76c7
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Fri, 18 Mar 2016 17:20:30 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sat, 19 Mar 2016 10:26:40 +0100

x86/topology: Use total_cpus not nr_cpu_ids for logical packages

nr_cpu_ids can be limited on the command line via nr_cpus=. That can break the
logical package management because it results in a smaller number of packages,
but the cpus to online are occupying the full package space as the hyper
threads are enumerated after the physical cores typically.

total_cpus is the real possible cpu space not limited by nr_cpus command line
and gives us the proper number of packages.

Reported-by: Mike Galbraith <umgwanakikbuti@...il.com>
Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Xiong Zhou <jencce.kernel@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Andreas Herrmann <aherrmann@...e.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603181254330.3978@nanos
---
 arch/x86/kernel/smpboot.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 81e6a43..b2c99f8 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -325,9 +325,14 @@ static void __init smp_init_package_map(void)
 	 * By not including this we'll sometimes over-estimate the number of
 	 * logical packages by the amount of !present siblings, but this is
 	 * still better than MAX_LOCAL_APIC.
+	 *
+	 * We use total_cpus not nr_cpu_ids because nr_cpu_ids can be limited
+	 * on the command line leading to a similar issue as the HT disable
+	 * problem because the hyperthreads are usually enumerated after the
+	 * primary cores.
 	 */
 	ncpus = boot_cpu_data.x86_max_cores;
-	__max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
+	__max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
 
 	/*
 	 * Possibly larger than what we need as the number of apic ids per