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authorPrarit Bhargava <prarit@redhat.com>2017-12-04 11:45:21 -0500
committerThomas Gleixner <tglx@linutronix.de>2017-12-07 10:28:22 +0100
commit947134d9b00f342415af7eddd42a5fce7262a1b9 (patch)
tree5b727713b606ec88fc5d085249526f48fa7c1dfb /arch/x86/kernel/smpboot.c
parent88edb57d1e0b262e669c5cad36646dcf5a7f37f5 (diff)
downloadlinux-947134d9b00f342415af7eddd42a5fce7262a1b9.tar.bz2
x86/smpboot: Do not use smp_num_siblings in __max_logical_packages calculation
Documentation/x86/topology.txt defines smp_num_siblings as "The number of threads in a core". Since commit bbb65d2d365e ("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: b4c0a7326f5d ("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
Diffstat (limited to 'arch/x86/kernel/smpboot.c')
-rw-r--r--arch/x86/kernel/smpboot.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 05a97d5fe298..35cb20994e32 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -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);