The ht flag indicates that a processor is capable of having sibling threads. This has long been confusing for users who confuse the ht flag as indicating that hyperthreading is enabled on their systems even though it may have been disabled in BIOS.
This patch removes the hyperthreading flag when no cpu thread siblings are found, ie) smp_num_siblings == 1. Cc: Oren Twaig <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: [email protected] Cc: Borislav Petkov <[email protected]> Cc: Paul Gortmaker <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Dave Jones <[email protected]> Cc: Torsten Kaiser <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Jan Kiszka <[email protected]> Cc: Toshi Kani <[email protected]> Cc: Andrew Jones <[email protected]> Signed-off-by: Prarit Bhargava <[email protected]> --- arch/x86/kernel/smpboot.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index e5ab30b..2eaadf0 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -371,6 +371,7 @@ void set_cpu_sibling_map(int cpu) cpumask_set_cpu(cpu, cpu_core_mask(cpu)); c->booted_cores = 1; smp_num_siblings = 1; + clear_cpu_cap(c, X86_FEATURE_HT); return; } @@ -419,6 +420,9 @@ void set_cpu_sibling_map(int cpu) /* Only need to check this on the boot cpu, o/w it is disabled */ if (cpu == 0) smp_num_siblings = cpumask_weight(cpu_sibling_mask(cpu)); + + if (cpu_has_ht && smp_num_siblings == 1) + clear_cpu_cap(c, X86_FEATURE_HT); } /* maps the cpu to the sched domain representing multi-core */ -- 1.7.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
