The smt-enabled kernel parameter basically leaves unwanted cpus executing
in firmware or wherever they happen to be. The very same applies to the
ibm,smt-enabled DT property which is no more used by anything known. These
are hacks that shoudn't be used in a production environment.
Quoting mpe, "there are better ways for firmware to disable SMT".
It also has an evil side effect on the split-core feature for powernv. The
code needs all the cpus to participate to the split mode update: it relies
on smp_send_reschedule() to get offline ones to do so. This doesn't work with
cpus that haven't come up... The consequence is a kernel hang on powernv when
trying to limit the number of hw threads at boot time (e.g. smt-enabled to
anything but 8 on POWER8).
This patch simply removes both the smt-enabled kernel parameter and the
ibm,smt-enabled property for all platforms. The new default is to start
all hw threads. That leaves /sys the only supported API to change SMT
settings.
Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---
v2: also drop ibm,smt-enabled
arch/powerpc/kernel/setup_64.c | 46 ----------------------------------------
1 file changed, 46 deletions(-)
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 49f553b..29c1845 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -131,57 +131,11 @@ static void setup_tlb_core_data(void)
#ifdef CONFIG_SMP
-static char *smt_enabled_cmdline;
-
-/* Look for ibm,smt-enabled OF option */
static void check_smt_enabled(void)
{
- struct device_node *dn;
- const char *smt_option;
-
/* Default to enabling all threads */
smt_enabled_at_boot = threads_per_core;
-
- /* Allow the command line to overrule the OF option */
- if (smt_enabled_cmdline) {
- if (!strcmp(smt_enabled_cmdline, "on"))
- smt_enabled_at_boot = threads_per_core;
- else if (!strcmp(smt_enabled_cmdline, "off"))
- smt_enabled_at_boot = 0;
- else {
- int smt;
- int rc;
-
- rc = kstrtoint(smt_enabled_cmdline, 10, &smt);
- if (!rc)
- smt_enabled_at_boot =
- min(threads_per_core, smt);
- }
- } else {
- dn = of_find_node_by_path("/options");
- if (dn) {
- smt_option = of_get_property(dn, "ibm,smt-enabled",
- NULL);
-
- if (smt_option) {
- if (!strcmp(smt_option, "on"))
- smt_enabled_at_boot = threads_per_core;
- else if (!strcmp(smt_option, "off"))
- smt_enabled_at_boot = 0;
- }
-
- of_node_put(dn);
- }
- }
-}
-
-/* Look for smt-enabled= cmdline option */
-static int __init early_smt_enabled(char *p)
-{
- smt_enabled_cmdline = p;
- return 0;
}
-early_param("smt-enabled", early_smt_enabled);
#else
#define check_smt_enabled()
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
