[tip:x86/urgent] x86/topology: Use total_cpus not nr_cpu_ids for logical packages

From: tip-bot for Thomas Gleixner
Date: Sat Mar 19 2016 - 05:36:00 EST

Commit-ID: 3e8db2246b434c6b18a6a9f09904038bddcf76c7
Gitweb: http://git.kernel.org/tip/3e8db2246b434c6b18a6a9f09904038bddcf76c7
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 18 Mar 2016 17:20:30 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxx>
Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Xiong Zhou <jencce.kernel@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andreas Herrmann <aherrmann@xxxxxxxx>
Link: alpine.DEB.2.11.1603181254330.3978@nanos">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