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, 8 insertions, 11 deletions

diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index 4685337fa7c6..fb0901ec4306 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -103,21 +103,18 @@ static int __init machine_kdump_pm_init(void)
 	return 0;
 }
 arch_initcall(machine_kdump_pm_init);
-#endif
 
 /*
  * Start kdump: We expect here that a store status has been done on our CPU
  */
 static void __do_machine_kdump(void *image)
 {
-#ifdef CONFIG_CRASH_DUMP
 	int (*start_kdump)(int) = (void *)((struct kimage *) image)->start;
 
-	setup_regs();
 	__load_psw_mask(PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA);
 	start_kdump(1);
-#endif
 }
+#endif
 
 /*
  * Check if kdump checksums are valid: We call purgatory with parameter "0"
@@ -249,18 +246,18 @@ static void __do_machine_kexec(void *data)
  */
 static void __machine_kexec(void *data)
 {
-	struct kimage *image = data;
-
 	__arch_local_irq_stosm(0x04); /* enable DAT */
 	pfault_fini();
 	tracing_off();
 	debug_locks_off();
-	if (image->type == KEXEC_TYPE_CRASH) {
+#ifdef CONFIG_CRASH_DUMP
+	if (((struct kimage *) data)->type == KEXEC_TYPE_CRASH) {
+
 		lgr_info_log();
-		s390_reset_system(__do_machine_kdump, data);
-	} else {
-		s390_reset_system(__do_machine_kexec, data);
-	}
+		s390_reset_system(setup_regs, __do_machine_kdump, data);
+	} else
+#endif
+		s390_reset_system(NULL, __do_machine_kexec, data);
 	disabled_wait((unsigned long) __builtin_return_address(0));
 }