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x86/smpboot: Do not use smp_num_siblings in __max_logical_packages calculation

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Documentation/x86/topology.txt defines smp_num_siblings as "The number of
threads in a core".  Since commit bbb65d2d36 ("x86: use cpuid vector 0xb
when available for detecting cpu topology") smp_num_siblings is the
maximum number of threads in a core.  If Simultaneous MultiThreading
(SMT) is disabled on a system, smp_num_siblings is 2 and not 1 as
expected.

Use topology_max_smt_threads(), which contains the active numer of threads,
in the __max_logical_packages calculation.

On a single socket, single core, single thread system __max_smt_threads has
not been updated when the __max_logical_packages calculation happens, so its
zero which makes the package estimate fail. Initialize it to one, which is
the minimum number of threads on a core.

[ tglx: Folded the __max_smt_threads fix in ]

Fixes: b4c0a7326f ("x86/smpboot: Fix __max_logical_packages estimate")
Reported-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Prarit Bhargava <prarit@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jakub Kicinski <kubakici@wp.pl>
Cc: netdev@vger.kernel.org
Cc: "netdev@vger.kernel.org"
Cc: Clark Williams <williams@redhat.com>
Link: https://lkml.kernel.org/r/20171204164521.17870-1-prarit@redhat.com
This commit is contained in:
Prarit Bhargava 2017-12-04 11:45:21 -05:00 committed by Thomas Gleixner
parent 88edb57d1e
commit 947134d9b0
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/smpboot.c
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@ -106,7 +106,7 @@ EXPORT_SYMBOL(__max_logical_packages);
static unsigned int logical_packages __read_mostly;
/* Maximum number of SMT threads on any online core */
int __max_smt_threads __read_mostly;
int __read_mostly __max_smt_threads = 1;
/* Flag to indicate if a complete sched domain rebuild is required */
bool x86_topology_update;
@ -1304,7 +1304,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
* Today neither Intel nor AMD support heterogenous systems so
* extrapolate the boot cpu's data to all packages.
*/
ncpus = cpu_data(0).booted_cores * smp_num_siblings;
ncpus = cpu_data(0).booted_cores * topology_max_smt_threads();
__max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
pr_info("Max logical packages: %u\n", __max_logical_packages);