[PATCH] x86: Add topology_hw_smt_threads() and remove smp_num_siblings

From: Prarit Bhargava
Date: Thu Jan 04 2018 - 06:27:09 EST

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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@xxxxxxxxxx>
---
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
--
2.15.0.rc0.39.g2f0e14e64

Next message: Jon Hunter: "[PATCH] drm/nouveau/bar/gk20a: Avoid bar teardown during init"
Previous message: Pavel Machek: "Re: Avoid speculative indirect calls in kernel"
Next in thread: Prarit Bhargava: "Re: [PATCH] x86: Add topology_hw_smt_threads() and remove smp_num_siblings"
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