diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2018-05-29 17:50:22 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-15 18:12:51 +0200 |
| commit | b84b9184651dd2a003459293ec7caa58e5423562 (patch) | |
| tree | 34a78b6f4e404118fc3a7cbb9c7ce3a78170a2ad /arch/x86/kernel/smpboot.c | |
| parent | fc890e9b571fb273e714bae5de682226eaed9cb2 (diff) | |
x86/smp: Provide topology_is_primary_thread()
commit 6a4d2657e048f096c7ffcad254010bd94891c8c0 upstream
If the CPU is supporting SMT then the primary thread can be found by
checking the lower APIC ID bits for zero. smp_num_siblings is used to build
the mask for the APIC ID bits which need to be taken into account.
This uses the MPTABLE or ACPI/MADT supplied APIC ID, which can be different
than the initial APIC ID in CPUID. But according to AMD the lower bits have
to be consistent. Intel gave a tentative confirmation as well.
Preparatory patch to support disabling SMT at boot/runtime.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel/smpboot.c')
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 344d3c160f8d..e817e0904254 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -312,6 +312,15 @@ found: } /** + * topology_is_primary_thread - Check whether CPU is the primary SMT thread + * @cpu: CPU to check + */ +bool topology_is_primary_thread(unsigned int cpu) +{ + return apic_id_is_primary_thread(per_cpu(x86_cpu_to_apicid, cpu)); +} + +/** * topology_phys_to_logical_pkg - Map a physical package id to a logical * * Returns logical package id or -1 if not found |