Commit cc6810e3 authored by Linus Torvalds's avatar Linus Torvalds

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

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
parents 58f6d428 b284909a
...@@ -71,7 +71,7 @@ void __init check_bugs(void) ...@@ -71,7 +71,7 @@ void __init check_bugs(void)
* identify_boot_cpu() initialized SMT support information, let the * identify_boot_cpu() initialized SMT support information, let the
* core code know. * core code know.
*/ */
cpu_smt_check_topology_early(); cpu_smt_check_topology();
if (!IS_ENABLED(CONFIG_SMP)) { if (!IS_ENABLED(CONFIG_SMP)) {
pr_info("CPU: "); pr_info("CPU: ");
......
...@@ -26,6 +26,7 @@ ...@@ -26,6 +26,7 @@
#include <linux/mod_devicetable.h> #include <linux/mod_devicetable.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/sched/smt.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/tboot.h> #include <linux/tboot.h>
#include <linux/trace_events.h> #include <linux/trace_events.h>
...@@ -6823,7 +6824,7 @@ static int vmx_vm_init(struct kvm *kvm) ...@@ -6823,7 +6824,7 @@ static int vmx_vm_init(struct kvm *kvm)
* Warn upon starting the first VM in a potentially * Warn upon starting the first VM in a potentially
* insecure environment. * insecure environment.
*/ */
if (cpu_smt_control == CPU_SMT_ENABLED) if (sched_smt_active())
pr_warn_once(L1TF_MSG_SMT); pr_warn_once(L1TF_MSG_SMT);
if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER) if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER)
pr_warn_once(L1TF_MSG_L1D); pr_warn_once(L1TF_MSG_L1D);
......
...@@ -180,12 +180,10 @@ enum cpuhp_smt_control { ...@@ -180,12 +180,10 @@ enum cpuhp_smt_control {
#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT) #if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
extern enum cpuhp_smt_control cpu_smt_control; extern enum cpuhp_smt_control cpu_smt_control;
extern void cpu_smt_disable(bool force); extern void cpu_smt_disable(bool force);
extern void cpu_smt_check_topology_early(void);
extern void cpu_smt_check_topology(void); extern void cpu_smt_check_topology(void);
#else #else
# define cpu_smt_control (CPU_SMT_ENABLED) # define cpu_smt_control (CPU_SMT_ENABLED)
static inline void cpu_smt_disable(bool force) { } 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) { } static inline void cpu_smt_check_topology(void) { }
#endif #endif
......
...@@ -376,9 +376,6 @@ void __weak arch_smt_update(void) { } ...@@ -376,9 +376,6 @@ void __weak arch_smt_update(void) { }
#ifdef CONFIG_HOTPLUG_SMT #ifdef CONFIG_HOTPLUG_SMT
enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED; 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) void __init cpu_smt_disable(bool force)
{ {
...@@ -397,25 +394,11 @@ 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 * The decision whether SMT is supported can only be done after the full
* CPU identification. Called from architecture code before non boot CPUs * CPU identification. Called from architecture code.
* 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.
*/ */
void __init cpu_smt_check_topology(void) void __init cpu_smt_check_topology(void)
{ {
if (!cpu_smt_available) if (!topology_smt_supported())
cpu_smt_control = CPU_SMT_NOT_SUPPORTED; cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
} }
...@@ -428,18 +411,10 @@ early_param("nosmt", smt_cmdline_disable); ...@@ -428,18 +411,10 @@ early_param("nosmt", smt_cmdline_disable);
static inline bool cpu_smt_allowed(unsigned int cpu) static inline bool cpu_smt_allowed(unsigned int cpu)
{ {
if (topology_is_primary_thread(cpu)) if (cpu_smt_control == CPU_SMT_ENABLED)
return true; return true;
/* if (topology_is_primary_thread(cpu))
* 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)
return true; return true;
/* /*
...@@ -2090,10 +2065,8 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) ...@@ -2090,10 +2065,8 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
*/ */
cpuhp_offline_cpu_device(cpu); cpuhp_offline_cpu_device(cpu);
} }
if (!ret) { if (!ret)
cpu_smt_control = ctrlval; cpu_smt_control = ctrlval;
arch_smt_update();
}
cpu_maps_update_done(); cpu_maps_update_done();
return ret; return ret;
} }
...@@ -2104,7 +2077,6 @@ static int cpuhp_smt_enable(void) ...@@ -2104,7 +2077,6 @@ static int cpuhp_smt_enable(void)
cpu_maps_update_begin(); cpu_maps_update_begin();
cpu_smt_control = CPU_SMT_ENABLED; cpu_smt_control = CPU_SMT_ENABLED;
arch_smt_update();
for_each_present_cpu(cpu) { for_each_present_cpu(cpu) {
/* Skip online CPUs and CPUs on offline nodes */ /* Skip online CPUs and CPUs on offline nodes */
if (cpu_online(cpu) || !node_online(cpu_to_node(cpu))) if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
......
...@@ -5980,6 +5980,7 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p ...@@ -5980,6 +5980,7 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
#ifdef CONFIG_SCHED_SMT #ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present); DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
static inline void set_idle_cores(int cpu, int val) static inline void set_idle_cores(int cpu, int val)
{ {
......
...@@ -584,8 +584,6 @@ void __init smp_init(void) ...@@ -584,8 +584,6 @@ void __init smp_init(void)
num_nodes, (num_nodes > 1 ? "s" : ""), num_nodes, (num_nodes > 1 ? "s" : ""),
num_cpus, (num_cpus > 1 ? "s" : "")); num_cpus, (num_cpus > 1 ? "s" : ""));
/* Final decision about SMT support */
cpu_smt_check_topology();
/* Any cleanup work */ /* Any cleanup work */
smp_cpus_done(setup_max_cpus); smp_cpus_done(setup_max_cpus);
} }
......
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