Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

Pull cpu hotplug fixes from Thomas Gleixner:
 "Two fixes for the cpu hotplug machinery:

   - Replace the overly clever 'SMT disabled by BIOS' detection logic as
     it breaks KVM scenarios and prevents speculation control updates
     when the Hyperthreads are brought online late after boot.

   - Remove a redundant invocation of the speculation control update
     function"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM
  x86/speculation: Remove redundant arch_smt_update() invocation

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1de0f41..01874d5 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -71,7 +71,7 @@ void __init check_bugs(void)
         * identify_boot_cpu() initialized SMT support information, let the
         * core code know.
         */
-       cpu_smt_check_topology_early();
+       cpu_smt_check_topology();
 
        if (!IS_ENABLED(CONFIG_SMP)) {
                pr_info("CPU: ");

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4341175..95d6180 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -26,6 +26,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
+#include <linux/sched/smt.h>
 #include <linux/slab.h>
 #include <linux/tboot.h>
 #include <linux/trace_events.h>
@@ -6823,7 +6824,7 @@ static int vmx_vm_init(struct kvm *kvm)
                         * Warn upon starting the first VM in a potentially
                         * insecure environment.
                         */
-                       if (cpu_smt_control == CPU_SMT_ENABLED)
+                       if (sched_smt_active())
                                pr_warn_once(L1TF_MSG_SMT);
                        if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER)
                                pr_warn_once(L1TF_MSG_L1D);

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 218df7f..5041357 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -180,12 +180,10 @@ enum cpuhp_smt_control {
 #if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
 extern enum cpuhp_smt_control cpu_smt_control;
 extern void cpu_smt_disable(bool force);
-extern void cpu_smt_check_topology_early(void);
 extern void cpu_smt_check_topology(void);
 #else
 # define cpu_smt_control               (CPU_SMT_ENABLED)
 static inline void cpu_smt_disable(bool force) { }
-static inline void cpu_smt_check_topology_early(void) { }
 static inline void cpu_smt_check_topology(void) { }
 #endif
 

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 91d5c38..d1c6d15 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -376,9 +376,6 @@ void __weak arch_smt_update(void) { }
 
 #ifdef CONFIG_HOTPLUG_SMT
 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
-EXPORT_SYMBOL_GPL(cpu_smt_control);
-
-static bool cpu_smt_available __read_mostly;
 
 void __init cpu_smt_disable(bool force)
 {
@@ -397,25 +394,11 @@ void __init cpu_smt_disable(bool force)
 
 /*
  * The decision whether SMT is supported can only be done after the full
- * CPU identification. Called from architecture code before non boot CPUs
- * are brought up.
- */
-void __init cpu_smt_check_topology_early(void)
-{
-       if (!topology_smt_supported())
-               cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
-}
-
-/*
- * If SMT was disabled by BIOS, detect it here, after the CPUs have been
- * brought online. This ensures the smt/l1tf sysfs entries are consistent
- * with reality. cpu_smt_available is set to true during the bringup of non
- * boot CPUs when a SMT sibling is detected. Note, this may overwrite
- * cpu_smt_control's previous setting.
+ * CPU identification. Called from architecture code.
  */
 void __init cpu_smt_check_topology(void)
 {
-       if (!cpu_smt_available)
+       if (!topology_smt_supported())
                cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 }
 
@@ -428,18 +411,10 @@ early_param("nosmt", smt_cmdline_disable);
 
 static inline bool cpu_smt_allowed(unsigned int cpu)
 {
-       if (topology_is_primary_thread(cpu))
+       if (cpu_smt_control == CPU_SMT_ENABLED)
                return true;
 
-       /*
-        * If the CPU is not a 'primary' thread and the booted_once bit is
-        * set then the processor has SMT support. Store this information
-        * for the late check of SMT support in cpu_smt_check_topology().
-        */
-       if (per_cpu(cpuhp_state, cpu).booted_once)
-               cpu_smt_available = true;
-
-       if (cpu_smt_control == CPU_SMT_ENABLED)
+       if (topology_is_primary_thread(cpu))
                return true;
 
        /*
@@ -2090,10 +2065,8 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
                 */
                cpuhp_offline_cpu_device(cpu);
        }
-       if (!ret) {
+       if (!ret)
                cpu_smt_control = ctrlval;
-               arch_smt_update();
-       }
        cpu_maps_update_done();
        return ret;
 }
@@ -2104,7 +2077,6 @@ static int cpuhp_smt_enable(void)
 
        cpu_maps_update_begin();
        cpu_smt_control = CPU_SMT_ENABLED;
-       arch_smt_update();
        for_each_present_cpu(cpu) {
                /* Skip online CPUs and CPUs on offline nodes */
                if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 50aa2ab..310d063 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5980,6 +5980,7 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
 
 #ifdef CONFIG_SCHED_SMT
 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
+EXPORT_SYMBOL_GPL(sched_smt_present);
 
 static inline void set_idle_cores(int cpu, int val)
 {

diff --git a/kernel/smp.c b/kernel/smp.c
index 163c451..f4cf1b0 100644 (file)
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -584,8 +584,6 @@ void __init smp_init(void)
                num_nodes, (num_nodes > 1 ? "s" : ""),
                num_cpus,  (num_cpus  > 1 ? "s" : ""));
 
-       /* Final decision about SMT support */
-       cpu_smt_check_topology();
        /* Any cleanup work */
        smp_cpus_done(setup_max_cpus);
 }