4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner tglx@linutronix.de
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: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/apic.h | 7 +++++++ arch/x86/include/asm/topology.h | 4 +++- arch/x86/kernel/apic/apic.c | 15 +++++++++++++++ arch/x86/kernel/smpboot.c | 9 +++++++++ 4 files changed, 34 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -633,6 +633,13 @@ extern int default_check_phys_apicid_pre #endif
#endif /* CONFIG_X86_LOCAL_APIC */ + +#ifdef CONFIG_SMP +bool apic_id_is_primary_thread(unsigned int id); +#else +static inline bool apic_id_is_primary_thread(unsigned int id) { return false; } +#endif + extern void irq_enter(void); extern void irq_exit(void);
--- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -129,13 +129,15 @@ static inline int topology_max_smt_threa }
int topology_update_package_map(unsigned int apicid, unsigned int cpu); -extern int topology_phys_to_logical_pkg(unsigned int pkg); +int topology_phys_to_logical_pkg(unsigned int pkg); +bool topology_is_primary_thread(unsigned int cpu); #else #define topology_max_packages() (1) static inline int topology_update_package_map(unsigned int apicid, unsigned int cpu) { return 0; } static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } static inline int topology_max_smt_threads(void) { return 1; } +static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } #endif
static inline void arch_fix_phys_package_id(int num, u32 slot) --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -2041,6 +2041,21 @@ static int cpuid_to_apicid[] = { [0 ... NR_CPUS - 1] = -1, };
+/** + * apic_id_is_primary_thread - Check whether APIC ID belongs to a primary thread + * @id: APIC ID to check + */ +bool apic_id_is_primary_thread(unsigned int apicid) +{ + u32 mask; + + if (smp_num_siblings == 1) + return true; + /* Isolate the SMT bit(s) in the APICID and check for 0 */ + mask = (1U << (fls(smp_num_siblings) - 1)) - 1; + return !(apicid & mask); +} + /* * Should use this API to allocate logical CPU IDs to keep nr_logical_cpuids * and cpuid_to_apicid[] synchronized. --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -296,6 +296,15 @@ 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