Date:   Thu, 4 Jan 2018 06:50:46 -0500
From:   Prarit Bhargava <prarit@...hat.com>
To:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Add topology_hw_smt_threads() and remove
 smp_num_siblings

Oops.  Forgot to cc everyone.

Please ignore.

P.

On 01/04/2018 06:26 AM, Prarit Bhargava wrote:
> Commit bbb65d2d365e ("x86: use cpuid vector 0xb when available for
> detecting cpu topology") changed the value of smp_num_siblings from the
> active number of threads in a core to the maximum number threads in a
> core.  e.g.) On Intel Haswell and newer systems smp_num_siblings is
> two even if SMT is disabled.
> 
> topology_max_smt_threads() already returns the active number of threads.
> Introduce topology_hw_smt_threads() which returns the maximum number of
> threads.  These are used to fix and replace references to smp_num_siblings.
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> ---
>  Documentation/x86/topology.txt          | 13 +++++++++----
>  arch/x86/include/asm/perf_event_p4.h    |  4 ++--
>  arch/x86/include/asm/smp.h              |  2 --
>  arch/x86/include/asm/topology.h         | 10 +++++-----
>  arch/x86/kernel/cpu/amd.c               |  6 ++----
>  arch/x86/kernel/cpu/common.c            | 18 +++++++++++-------
>  arch/x86/kernel/cpu/mcheck/mce-inject.c |  3 ++-
>  arch/x86/kernel/cpu/topology.c          |  4 ++--
>  arch/x86/kernel/itmt.c                  |  2 +-
>  arch/x86/kernel/process.c               |  3 ++-
>  arch/x86/kernel/smpboot.c               | 22 ++++++++--------------
>  arch/x86/oprofile/nmi_int.c             |  2 +-
>  arch/x86/oprofile/op_model_p4.c         |  4 ++--
>  13 files changed, 47 insertions(+), 46 deletions(-)
> 
> diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt
> index f3e9d7e9ed6c..9fa07a4460df 100644
> --- a/Documentation/x86/topology.txt
> +++ b/Documentation/x86/topology.txt
> @@ -83,13 +83,18 @@ The topology of a system is described in the units of:
>  
>    Core-related topology information in the kernel:
>  
> -  - smp_num_siblings:
> +  - topology_hw_smt_threads:
>  
> -    The number of threads in a core. The number of threads in a package can be
> -    calculated by:
> +    The maximum number of threads that a core's hardware supports.  For
> +    example, on Intel Haswell and newer systems this is 2 even if SMT is
> +    disabled.
>  
> -	threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
> +  - topology_max_smt_threads:
>  
> +    The number of threads/core available at runtime.  The number of threads in
> +    a package can be calculated by:
> +
> +    threads_per_package = cpuinfo_x86.x86_max_cores * topology_max_smt_threads
>  
>  * Threads:
>  
> diff --git a/arch/x86/include/asm/perf_event_p4.h b/arch/x86/include/asm/perf_event_p4.h
> index 94de1a05aeba..11afdadce9c2 100644
> --- a/arch/x86/include/asm/perf_event_p4.h
> +++ b/arch/x86/include/asm/perf_event_p4.h
> @@ -181,7 +181,7 @@ static inline u64 p4_clear_ht_bit(u64 config)
>  static inline int p4_ht_active(void)
>  {
>  #ifdef CONFIG_SMP
> -	return smp_num_siblings > 1;
> +	return topology_max_smt_threads() > 1;
>  #endif
>  	return 0;
>  }
> @@ -189,7 +189,7 @@ static inline int p4_ht_active(void)
>  static inline int p4_ht_thread(int cpu)
>  {
>  #ifdef CONFIG_SMP
> -	if (smp_num_siblings == 2)
> +	if (topology_max_smt_threads() == 2)
>  		return cpu != cpumask_first(this_cpu_cpumask_var_ptr(cpu_sibling_map));
>  #endif
>  	return 0;
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 461f53d27708..cf28a3932917 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -18,7 +18,6 @@
>  #include <asm/thread_info.h>
>  #include <asm/cpumask.h>
>  
> -extern int smp_num_siblings;
>  extern unsigned int num_processors;
>  
>  DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map);
> @@ -170,7 +169,6 @@ static inline int wbinvd_on_all_cpus(void)
>  	wbinvd();
>  	return 0;
>  }
> -#define smp_num_siblings	1
>  #endif /* CONFIG_SMP */
>  
>  extern unsigned disabled_cpus;
> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> index c1d2a9892352..b5ff1c784eef 100644
> --- a/arch/x86/include/asm/topology.h
> +++ b/arch/x86/include/asm/topology.h
> @@ -116,16 +116,16 @@ extern unsigned int __max_logical_packages;
>  #define topology_max_packages()			(__max_logical_packages)
>  
>  extern int __max_smt_threads;
> -
> -static inline int topology_max_smt_threads(void)
> -{
> -	return __max_smt_threads;
> -}
> +#define topology_max_smt_threads()		(__max_smt_threads)
> +extern int __hw_smt_threads;
> +#define topology_hw_smt_threads()		(__hw_smt_threads)
>  
>  int topology_update_package_map(unsigned int apicid, unsigned int cpu);
>  extern int topology_phys_to_logical_pkg(unsigned int pkg);
>  #else
>  #define topology_max_packages()			(1)
> +#define topology_max_smt_threads()		(1)
> +#define topology_hw_smt_threads()		(1)
>  static inline int
>  topology_update_package_map(unsigned int apicid, unsigned int cpu) { return 0; }
>  static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index bcb75dc97d44..f2582505e2f9 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -332,16 +332,14 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
>  		cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
>  
>  		node_id  = ecx & 0xff;
> -		smp_num_siblings = ((ebx >> 8) & 0xff) + 1;
> +		__hw_smt_threads = ((ebx >> 8) & 0xff) + 1;
>  
>  		if (c->x86 == 0x15)
>  			c->cu_id = ebx & 0xff;
>  
>  		if (c->x86 >= 0x17) {
>  			c->cpu_core_id = ebx & 0xff;
> -
> -			if (smp_num_siblings > 1)
> -				c->x86_max_cores /= smp_num_siblings;
> +			c->x86_max_cores /= topology_hw_smt_threads();
>  		}
>  
>  		/*
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index c47de4ebf63a..1070e2832ca3 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -654,22 +654,22 @@ void detect_ht(struct cpuinfo_x86 *c)
>  
>  	cpuid(1, &eax, &ebx, &ecx, &edx);
>  
> -	smp_num_siblings = (ebx & 0xff0000) >> 16;
> +	__hw_smt_threads = (ebx & 0xff0000) >> 16;
>  
> -	if (smp_num_siblings == 1) {
> +	if (topology_hw_smt_threads() == 1) {
>  		pr_info_once("CPU0: Hyper-Threading is disabled\n");
>  		goto out;
>  	}
>  
> -	if (smp_num_siblings <= 1)
> +	if (topology_hw_smt_threads() <= 1)
>  		goto out;
>  
> -	index_msb = get_count_order(smp_num_siblings);
> +	index_msb = get_count_order(topology_hw_smt_threads());
>  	c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid, index_msb);
>  
> -	smp_num_siblings = smp_num_siblings / c->x86_max_cores;
> +	__hw_smt_threads = topology_hw_smt_threads() / c->x86_max_cores;
>  
> -	index_msb = get_count_order(smp_num_siblings);
> +	index_msb = get_count_order(topology_hw_smt_threads());
>  
>  	core_bits = get_count_order(c->x86_max_cores);
>  
> @@ -677,7 +677,7 @@ void detect_ht(struct cpuinfo_x86 *c)
>  				       ((1 << core_bits) - 1);
>  
>  out:
> -	if (!printed && (c->x86_max_cores * smp_num_siblings) > 1) {
> +	if (!printed && (c->x86_max_cores * topology_hw_smt_threads()) > 1) {
>  		pr_info("CPU: Physical Processor ID: %d\n",
>  			c->phys_proc_id);
>  		pr_info("CPU: Processor Core ID: %d\n",
> @@ -1228,6 +1228,10 @@ static void identify_cpu(struct cpuinfo_x86 *c)
>  	/* Init Machine Check Exception if available. */
>  	mcheck_cpu_init(c);
>  
> +	/* Must be called before select_idle_routine */
> +	if (c != &boot_cpu_data)
> +		set_cpu_sibling_map(raw_smp_processor_id());
> +
>  	select_idle_routine(c);
>  
>  #ifdef CONFIG_NUMA
> diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> index 231ad23b24a9..3785929d11af 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> @@ -420,7 +420,8 @@ static u32 get_nbc_for_node(int node_id)
>  	struct cpuinfo_x86 *c = &boot_cpu_data;
>  	u32 cores_per_node;
>  
> -	cores_per_node = (c->x86_max_cores * smp_num_siblings) / amd_get_nodes_per_socket();
> +	cores_per_node = (c->x86_max_cores * topology_hw_smt_threads()) /
> +			 amd_get_nodes_per_socket();
>  
>  	return cores_per_node * node_id;
>  }
> diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
> index b099024d339c..8cf2927c73ec 100644
> --- a/arch/x86/kernel/cpu/topology.c
> +++ b/arch/x86/kernel/cpu/topology.c
> @@ -56,7 +56,7 @@ void detect_extended_topology(struct cpuinfo_x86 *c)
>  	/*
>  	 * Populate HT related information from sub-leaf level 0.
>  	 */
> -	core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
> +	core_level_siblings = __hw_smt_threads = LEVEL_MAX_SIBLINGS(ebx);
>  	core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
>  
>  	sub_index = 1;
> @@ -85,7 +85,7 @@ void detect_extended_topology(struct cpuinfo_x86 *c)
>  	 */
>  	c->apicid = apic->phys_pkg_id(c->initial_apicid, 0);
>  
> -	c->x86_max_cores = (core_level_siblings / smp_num_siblings);
> +	c->x86_max_cores = (core_level_siblings / topology_hw_smt_threads());
>  
>  	if (!printed) {
>  		pr_info("CPU: Physical Processor ID: %d\n",
> diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c
> index f73f475d0573..4b887d3f79ed 100644
> --- a/arch/x86/kernel/itmt.c
> +++ b/arch/x86/kernel/itmt.c
> @@ -206,7 +206,7 @@ void sched_set_itmt_core_prio(int prio, int core_cpu)
>  		 * of the priority chain and only used when
>  		 * all other high priority cpus are out of capacity.
>  		 */
> -		smt_prio = prio * smp_num_siblings / i;
> +		smt_prio = prio * topology_hw_smt_threads() / i;
>  		per_cpu(sched_core_priority, cpu) = smt_prio;
>  		i++;
>  	}
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index aed9d94bd46f..67575faee8dd 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -476,7 +476,8 @@ static __cpuidle void mwait_idle(void)
>  void select_idle_routine(const struct cpuinfo_x86 *c)
>  {
>  #ifdef CONFIG_SMP
> -	if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1)
> +	if (boot_option_idle_override == IDLE_POLL &&
> +	    topology_hw_smt_threads() > 1)
>  		pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
>  #endif
>  	if (x86_idle || boot_option_idle_override == IDLE_POLL)
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index ed556d50d7ed..56bdcdba006f 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -79,10 +79,6 @@
>  #include <asm/misc.h>
>  #include <asm/qspinlock.h>
>  
> -/* Number of siblings per CPU package */
> -int smp_num_siblings = 1;
> -EXPORT_SYMBOL(smp_num_siblings);
> -
>  /* Last level cache ID of each logical CPU */
>  DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id) = BAD_APICID;
>  
> @@ -105,8 +101,11 @@ unsigned int __max_logical_packages __read_mostly;
>  EXPORT_SYMBOL(__max_logical_packages);
>  static unsigned int logical_packages __read_mostly;
>  
> -/* Maximum number of SMT threads on any online core */
> +/* Maximum number of SMT threads on any online core determined by topology */
>  int __read_mostly __max_smt_threads = 1;
> +/* Maximum number of SMT threads read from hardware */
> +int __read_mostly __hw_smt_threads = 1;
> +EXPORT_SYMBOL(__hw_smt_threads);
>  
>  /* Flag to indicate if a complete sched domain rebuild is required */
>  bool x86_topology_update;
> @@ -177,16 +176,11 @@ static void smp_callin(void)
>  	apic_ap_setup();
>  
>  	/*
> -	 * Save our processor parameters. Note: this information
> -	 * is needed for clock calibration.
> -	 */
> -	smp_store_cpu_info(cpuid);
> -
> -	/*
> -	 * The topology information must be up to date before
> +	 * Save CPU parameters and topology.  This information is needed for
> +	 * clock calibration, and must be update to date before calling
>  	 * calibrate_delay() and notify_cpu_starting().
>  	 */
> -	set_cpu_sibling_map(raw_smp_processor_id());
> +	smp_store_cpu_info(cpuid);
>  
>  	/*
>  	 * Get our bogomips.
> @@ -463,7 +457,7 @@ static bool x86_has_numa_in_package;
>  
>  void set_cpu_sibling_map(int cpu)
>  {
> -	bool has_smt = smp_num_siblings > 1;
> +	bool has_smt = topology_hw_smt_threads() > 1;
>  	bool has_mp = has_smt || boot_cpu_data.x86_max_cores > 1;
>  	struct cpuinfo_x86 *c = &cpu_data(cpu);
>  	struct cpuinfo_x86 *o;
> diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
> index 174c59774cc9..8029db4c4d3b 100644
> --- a/arch/x86/oprofile/nmi_int.c
> +++ b/arch/x86/oprofile/nmi_int.c
> @@ -566,7 +566,7 @@ static int __init p4_init(char **cpu_type)
>  	model = &op_p4_spec;
>  	return 1;
>  #else
> -	switch (smp_num_siblings) {
> +	switch (topology_hw_smt_threads()) {
>  	case 1:
>  		*cpu_type = "i386/p4";
>  		model = &op_p4_spec;
> diff --git a/arch/x86/oprofile/op_model_p4.c b/arch/x86/oprofile/op_model_p4.c
> index ad1d91f475ab..7bebd042df15 100644
> --- a/arch/x86/oprofile/op_model_p4.c
> +++ b/arch/x86/oprofile/op_model_p4.c
> @@ -43,7 +43,7 @@ static unsigned int num_controls = NUM_CONTROLS_NON_HT;
>  static inline void setup_num_counters(void)
>  {
>  #ifdef CONFIG_SMP
> -	if (smp_num_siblings == 2) {
> +	if (topology_hw_smt_threads() == 2) {
>  		num_counters = NUM_COUNTERS_HT2;
>  		num_controls = NUM_CONTROLS_HT2;
>  	}
> @@ -53,7 +53,7 @@ static inline void setup_num_counters(void)
>  static inline int addr_increment(void)
>  {
>  #ifdef CONFIG_SMP
> -	return smp_num_siblings == 2 ? 2 : 1;
> +	return topology_hw_smt_threads() == 2 ? 2 : 1;
>  #else
>  	return 1;
>  #endif
> 

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