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

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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
This commit is contained in:
Linus Torvalds 2019-02-03 09:02:03 -08:00
commit cc6810e36b
6 changed files with 9 additions and 39 deletions
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2
arch/x86/kernel/cpu/bugs.c
View File

@ -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: ");

3
arch/x86/kvm/vmx/vmx.c
View File

@ -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);

2
include/linux/cpu.h
View File

@ -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

38
kernel/cpu.c
View File

@ -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)))

1
kernel/sched/fair.c
View File

@ -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)
{

2
kernel/smp.c
View File

@ -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);
}