s390: add SMT support

The multi-threading facility is introduced with the z13 processor family.
This patch adds code to detect the multi-threading facility. With the
facility enabled each core will surface multiple hardware threads to the
system. Each hardware threads looks like a normal CPU to the operating
system with all its registers and properties.

The SCLP interface reports the SMT topology indirectly via the maximum
thread id. Each reported CPU in the result of a read-scp-information
is a core representing a number of hardware threads.

To reflect the reduced CPU capacity if two hardware threads run on a
single core the MT utilization counter set is used to normalize the
raw cputime obtained by the CPU timer deltas. This scaled cputime is
reported via the taskstats interface. The normal /proc/stat numbers
are based on the raw cputime and are not affected by the normalization.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 45 insertions, 18 deletions

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index b93bed76ea94..24ee33f1af24 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -59,32 +59,50 @@ static cpumask_t cpu_group_map(struct mask_info *info, unsigned int cpu)
 	return mask;
 }
 
-static struct mask_info *add_cpus_to_mask(struct topology_cpu *tl_cpu,
+static cpumask_t cpu_thread_map(unsigned int cpu)
+{
+	cpumask_t mask;
+	int i;
+
+	cpumask_copy(&mask, cpumask_of(cpu));
+	if (!topology_enabled || !MACHINE_HAS_TOPOLOGY)
+		return mask;
+	cpu -= cpu % (smp_cpu_mtid + 1);
+	for (i = 0; i <= smp_cpu_mtid; i++)
+		if (cpu_present(cpu + i))
+			cpumask_set_cpu(cpu + i, &mask);
+	return mask;
+}
+
+static struct mask_info *add_cpus_to_mask(struct topology_core *tl_core,
 					  struct mask_info *book,
 					  struct mask_info *socket,
 					  int one_socket_per_cpu)
 {
-	unsigned int cpu;
+	unsigned int core;
 
-	for_each_set_bit(cpu, &tl_cpu->mask[0], TOPOLOGY_CPU_BITS) {
-		unsigned int rcpu;
-		int lcpu;
+	for_each_set_bit(core, &tl_core->mask[0], TOPOLOGY_CORE_BITS) {
+		unsigned int rcore;
+		int lcpu, i;
 
-		rcpu = TOPOLOGY_CPU_BITS - 1 - cpu + tl_cpu->origin;
-		lcpu = smp_find_processor_id(rcpu);
+		rcore = TOPOLOGY_CORE_BITS - 1 - core + tl_core->origin;
+		lcpu = smp_find_processor_id(rcore << smp_cpu_mt_shift);
 		if (lcpu < 0)
 			continue;
-		cpumask_set_cpu(lcpu, &book->mask);
-		cpu_topology[lcpu].book_id = book->id;
-		cpumask_set_cpu(lcpu, &socket->mask);
-		cpu_topology[lcpu].core_id = rcpu;
-		if (one_socket_per_cpu) {
-			cpu_topology[lcpu].socket_id = rcpu;
-			socket = socket->next;
-		} else {
-			cpu_topology[lcpu].socket_id = socket->id;
+		for (i = 0; i <= smp_cpu_mtid; i++) {
+			cpu_topology[lcpu + i].book_id = book->id;
+			cpu_topology[lcpu + i].core_id = rcore;
+			cpu_topology[lcpu + i].thread_id = lcpu + i;
+			cpumask_set_cpu(lcpu + i, &book->mask);
+			cpumask_set_cpu(lcpu + i, &socket->mask);
+			if (one_socket_per_cpu)
+				cpu_topology[lcpu + i].socket_id = rcore;
+			else
+				cpu_topology[lcpu + i].socket_id = socket->id;
+			smp_cpu_set_polarization(lcpu + i, tl_core->pp);
 		}
-		smp_cpu_set_polarization(lcpu, tl_cpu->pp);
+		if (one_socket_per_cpu)
+			socket = socket->next;
 	}
 	return socket;
 }
@@ -108,7 +126,7 @@ static void clear_masks(void)
 static union topology_entry *next_tle(union topology_entry *tle)
 {
 	if (!tle->nl)
-		return (union topology_entry *)((struct topology_cpu *)tle + 1);
+		return (union topology_entry *)((struct topology_core *)tle + 1);
 	return (union topology_entry *)((struct topology_container *)tle + 1);
 }
 
@@ -231,9 +249,11 @@ static void update_cpu_masks(void)
 
 	spin_lock_irqsave(&topology_lock, flags);
 	for_each_possible_cpu(cpu) {
+		cpu_topology[cpu].thread_mask = cpu_thread_map(cpu);
 		cpu_topology[cpu].core_mask = cpu_group_map(&socket_info, cpu);
 		cpu_topology[cpu].book_mask = cpu_group_map(&book_info, cpu);
 		if (!MACHINE_HAS_TOPOLOGY) {
+			cpu_topology[cpu].thread_id = cpu;
 			cpu_topology[cpu].core_id = cpu;
 			cpu_topology[cpu].socket_id = cpu;
 			cpu_topology[cpu].book_id = cpu;
@@ -445,6 +465,12 @@ int topology_cpu_init(struct cpu *cpu)
 	return sysfs_create_group(&cpu->dev.kobj, &topology_cpu_attr_group);
 }
 
+const struct cpumask *cpu_thread_mask(int cpu)
+{
+	return &cpu_topology[cpu].thread_mask;
+}
+
+
 const struct cpumask *cpu_coregroup_mask(int cpu)
 {
 	return &cpu_topology[cpu].core_mask;
@@ -456,6 +482,7 @@ static const struct cpumask *cpu_book_mask(int cpu)
 }
 
 static struct sched_domain_topology_level s390_topology[] = {
+	{ cpu_thread_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
 	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
 	{ cpu_book_mask, SD_INIT_NAME(BOOK) },
 	{ cpu_cpu_mask, SD_INIT_NAME(DIE) },