powerpc/pseries: Do not start secondaries in Open Firmware
Starting secondary CPUs early on from Open Firmware and placing them
in a holding spin loop slows down the boot process significantly under
some hypervisors such as KVM.
This is also unnecessary when RTAS supports querying the CPU state
So let's not do it.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 12e656f..5fe2842 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -196,6 +196,8 @@
static cell_t __initdata regbuf[1024];
+static bool rtas_has_query_cpu_stopped;
+
/*
* Error results ... some OF calls will return "-1" on error, some
@@ -1574,6 +1576,11 @@
prom_setprop(rtas_node, "/rtas", "linux,rtas-entry",
&val, sizeof(val));
+ /* Check if it supports "query-cpu-stopped-state" */
+ if (prom_getprop(rtas_node, "query-cpu-stopped-state",
+ &val, sizeof(val)) != PROM_ERROR)
+ rtas_has_query_cpu_stopped = true;
+
#if defined(CONFIG_PPC_POWERNV) && defined(__BIG_ENDIAN__)
/* PowerVN takeover hack */
prom_rtas_data = base;
@@ -1815,6 +1822,18 @@
= (void *) LOW_ADDR(__secondary_hold_acknowledge);
unsigned long secondary_hold = LOW_ADDR(__secondary_hold);
+ /*
+ * On pseries, if RTAS supports "query-cpu-stopped-state",
+ * we skip this stage, the CPUs will be started by the
+ * kernel using RTAS.
+ */
+ if ((of_platform == PLATFORM_PSERIES ||
+ of_platform == PLATFORM_PSERIES_LPAR) &&
+ rtas_has_query_cpu_stopped) {
+ prom_printf("prom_hold_cpus: skipped\n");
+ return;
+ }
+
prom_debug("prom_hold_cpus: start...\n");
prom_debug(" 1) spinloop = 0x%x\n", (unsigned long)spinloop);
prom_debug(" 1) *spinloop = 0x%x\n", *spinloop);
@@ -3011,6 +3030,8 @@
* On non-powermacs, put all CPUs in spin-loops.
*
* PowerMacs use a different mechanism to spin CPUs
+ *
+ * (This must be done after instanciating RTAS)
*/
if (of_platform != PLATFORM_POWERMAC &&
of_platform != PLATFORM_OPAL)
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 1c1771a..24f58cb 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -233,17 +233,23 @@
alloc_bootmem_cpumask_var(&of_spin_mask);
- /* Mark threads which are still spinning in hold loops. */
- if (cpu_has_feature(CPU_FTR_SMT)) {
- for_each_present_cpu(i) {
- if (cpu_thread_in_core(i) == 0)
- cpumask_set_cpu(i, of_spin_mask);
- }
- } else {
- cpumask_copy(of_spin_mask, cpu_present_mask);
- }
+ /*
+ * Mark threads which are still spinning in hold loops
+ *
+ * We know prom_init will not have started them if RTAS supports
+ * query-cpu-stopped-state.
+ */
+ if (rtas_token("query-cpu-stopped-state") == RTAS_UNKNOWN_SERVICE) {
+ if (cpu_has_feature(CPU_FTR_SMT)) {
+ for_each_present_cpu(i) {
+ if (cpu_thread_in_core(i) == 0)
+ cpumask_set_cpu(i, of_spin_mask);
+ }
+ } else
+ cpumask_copy(of_spin_mask, cpu_present_mask);
- cpumask_clear_cpu(boot_cpuid, of_spin_mask);
+ cpumask_clear_cpu(boot_cpuid, of_spin_mask);
+ }
/* Non-lpar has additional take/give timebase */
if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {