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, 12 insertions, 3 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 06c6d9ab5a8d..7eba5b5723e9 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -396,17 +396,26 @@ config HOTPLUG_CPU
 	  can be controlled through /sys/devices/system/cpu/cpu#.
 	  Say N if you want to disable CPU hotplug.
 
+config SCHED_SMT
+	def_bool n
+
 config SCHED_MC
 	def_bool n
 
 config SCHED_BOOK
+	def_bool n
+
+config SCHED_TOPOLOGY
 	def_bool y
-	prompt "Book scheduler support"
+	prompt "Topology scheduler support"
 	depends on SMP
+	select SCHED_SMT
 	select SCHED_MC
+	select SCHED_BOOK
 	help
-	  Book scheduler support improves the CPU scheduler's decision making
-	  when dealing with machines that have several books.
+	  Topology scheduler support improves the CPU scheduler's decision
+	  making when dealing with machines that have multi-threading,
+	  multiple cores or multiple books.
 
 source kernel/Kconfig.preempt