From 947134d9b00f342415af7eddd42a5fce7262a1b9 Mon Sep 17 00:00:00 2001 From: Prarit Bhargava Date: Mon, 4 Dec 2017 11:45:21 -0500 Subject: [PATCH] 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 Signed-off-by: Prarit Bhargava Tested-by: Jakub Kicinski Cc: netdev@vger.kernel.org Cc: "netdev@vger.kernel.org" Cc: Clark Williams Link: https://lkml.kernel.org/r/20171204164521.17870-1-prarit@redhat.com --- arch/x86/kernel/smpboot.c | 4 ++-- 1 file 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);