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Commit e1572f1d authored Sep 16, 2019 by Vitaly Kuznetsov Committed by Paolo Bonzini Sep 24, 2019

cpu/SMT: create and export cpu_smt_possible()



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>

parent a073d7e3

include/linux/cpu.h

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -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

kernel/cpu.c

+9 −2

Original line number	Original line	Diff line number	Diff line
	@@ -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