Commit cc6810e3 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

arch/x86/kernel/cpu/bugs.c

+1 −1
Original line number Diff line number Diff line
@@ -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: ");

arch/x86/kvm/vmx/vmx.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

include/linux/cpu.h

+0 −2
Original line number Diff line number Diff line
@@ -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

kernel/cpu.c

+5 −33
Original line number Diff line number Diff line
@@ -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)))

kernel/sched/fair.c

+1 −0
Original line number Diff line number Diff line
@@ -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)

{

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