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cpu/SMT: create and export cpu_smt_possible()

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KVM needs to know if SMT is theoretically possible, this means it is
supported and not forcefully disabled ('nosmt=force'). Create and
export cpu_smt_possible() answering this question.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2019-09-16 18:22:56 +02:00 committed by Paolo Bonzini
parent a073d7e3ad
commit e1572f1d08
2 changed files with 11 additions and 2 deletions
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2
include/linux/cpu.h
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@ -201,12 +201,14 @@ enum cpuhp_smt_control {
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(void); extern void cpu_smt_check_topology(void);
extern bool cpu_smt_possible(void);
extern int cpuhp_smt_enable(void); extern int cpuhp_smt_enable(void);
extern int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval); extern int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval);
#else #else
# define cpu_smt_control (CPU_SMT_NOT_IMPLEMENTED) # define cpu_smt_control (CPU_SMT_NOT_IMPLEMENTED)
static inline void cpu_smt_disable(bool force) { } static inline void cpu_smt_disable(bool force) { }
static inline void cpu_smt_check_topology(void) { } static inline void cpu_smt_check_topology(void) { }
static inline bool cpu_smt_possible(void) { return false; }
static inline int cpuhp_smt_enable(void) { return 0; } static inline int cpuhp_smt_enable(void) { return 0; }
static inline int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { return 0; } static inline int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { return 0; }
#endif #endif

11
kernel/cpu.c
View File

@ -392,8 +392,7 @@ enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
void __init cpu_smt_disable(bool force) void __init cpu_smt_disable(bool force)
{ {
if (cpu_smt_control == CPU_SMT_FORCE_DISABLED || if (!cpu_smt_possible())
cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
return; return;
if (force) { if (force) {
@ -438,6 +437,14 @@ static inline bool cpu_smt_allowed(unsigned int cpu)
*/ */
return !cpumask_test_cpu(cpu, &cpus_booted_once_mask); return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
} }
/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
bool cpu_smt_possible(void)
{
return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
}
EXPORT_SYMBOL_GPL(cpu_smt_possible);
#else #else
static inline bool cpu_smt_allowed(unsigned int cpu) { return true; } static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
#endif #endif