Merge tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug updates from Thomas Gleixner:
 "Updates for the CPU hotplug core:

   - Support partial SMT enablement.

     So far the sysfs SMT control only allows to toggle between SMT on
     and off. That's sufficient for x86 which usually has at max two
     threads except for the Xeon PHI platform which has four threads per
     core

     Though PowerPC has up to 16 threads per core and so far it's only
     possible to control the number of enabled threads per core via a
     command line option. There is some way to control this at runtime,
     but that lacks enforcement and the usability is awkward

     This update expands the sysfs interface and the core infrastructure
     to accept numerical values so PowerPC can build SMT runtime control
     for partial SMT enablement on top

     The core support has also been provided to the PowerPC maintainers
     who added the PowerPC related changes on top

   - Minor cleanups and documentation updates"

* tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation: core-api/cpuhotplug: Fix state names
  cpu/hotplug: Remove unused function declaration cpu_set_state_online()
  cpu/SMT: Fix cpu_smt_possible() comment
  cpu/SMT: Allow enabling partial SMT states via sysfs
  cpu/SMT: Create topology_smt_thread_allowed()
  cpu/SMT: Remove topology_smt_supported()
  cpu/SMT: Store the current/max number of threads
  cpu/SMT: Move smt/control simple exit cases earlier
  cpu/SMT: Move SMT prototypes into cpu_smt.h
  cpu/hotplug: Remove dependancy against cpu_primary_thread_mask

4 files changed, 6 insertions, 11 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af2..63c5d6a2022b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -34,6 +34,9 @@ config ARCH_HAS_SUBPAGE_FAULTS
 config HOTPLUG_SMT
 	bool
 
+config SMT_NUM_THREADS_DYNAMIC
+	bool
+
 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
 config HOTPLUG_CORE_SYNC
 	bool
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index caf41c4869a0..3235ba1e5b06 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -136,10 +136,11 @@ static inline int topology_max_smt_threads(void)
 	return __max_smt_threads;
 }
 
+#include <linux/cpu_smt.h>
+
 int topology_update_package_map(unsigned int apicid, unsigned int cpu);
 int topology_update_die_map(unsigned int dieid, unsigned int cpu);
 int topology_phys_to_logical_pkg(unsigned int pkg);
-bool topology_smt_supported(void);
 
 extern struct cpumask __cpu_primary_thread_mask;
 #define cpu_primary_thread_mask ((const struct cpumask *)&__cpu_primary_thread_mask)
@@ -162,7 +163,6 @@ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
 static inline int topology_max_die_per_package(void) { return 1; }
 static inline int topology_max_smt_threads(void) { return 1; }
 static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }
-static inline bool topology_smt_supported(void) { return false; }
 #endif /* !CONFIG_SMP */
 
 static inline void arch_fix_phys_package_id(int num, u32 slot)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index e3a65e9fc750..281fc3f6ea6b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2343,7 +2343,7 @@ void __init arch_cpu_finalize_init(void)
 	 * identify_boot_cpu() initialized SMT support information, let the
 	 * core code know.
 	 */
-	cpu_smt_check_topology();
+	cpu_smt_set_num_threads(smp_num_siblings, smp_num_siblings);
 
 	if (!IS_ENABLED(CONFIG_SMP)) {
 		pr_info("CPU: ");
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index e1aa2cd7734b..d4e897b820c4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -327,14 +327,6 @@ static void notrace start_secondary(void *unused)
 }
 
 /**
- * topology_smt_supported - Check whether SMT is supported by the CPUs
- */
-bool topology_smt_supported(void)
-{
-	return smp_num_siblings > 1;
-}
-
-/**
  * topology_phys_to_logical_pkg - Map a physical package id to a logical
  * @phys_pkg:	The physical package id to map
  *