Provide a generic smt parameters interface aligned with s390
to allow users to limit smt usage and threads per core.
It replaced previous undocumented "nothreads" parameter for
smp-cps which is ambiguous and does not cover smp-mt.
Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 4 ++--
arch/mips/include/asm/smp.h | 2 ++
arch/mips/kernel/smp-cps.c | 13 +------------
arch/mips/kernel/smp-mt.c | 3 ++-
arch/mips/kernel/smp.c | 18 ++++++++++++++++++
5 files changed, 25 insertions(+), 15 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 91963d3f0d5c..515cd1f88ea2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3830,7 +3830,7 @@
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
and disable the IO APIC. legacy for "maxcpus=0".
- nosmt [KNL,S390] Disable symmetric multithreading (SMT).
+ nosmt [KNL,MIPS,S390] Disable symmetric multithreading (SMT).
Equivalent to smt=1.
[KNL,X86] Disable symmetric multithreading (SMT).
@@ -5743,7 +5743,7 @@
1: Fast pin select (default)
2: ATC IRMode
- smt= [KNL,S390] Set the maximum number of threads (logical
+ smt= [KNL,MIPS,S390] Set the maximum number of threads (logical
CPUs) to use per physical CPU on systems capable of
symmetric multithreading (SMT). Will be capped to the
actual hardware limit.
diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
index aab8981bc32c..a40d8c0e4b87 100644
--- a/arch/mips/include/asm/smp.h
+++ b/arch/mips/include/asm/smp.h
@@ -57,6 +57,8 @@ extern int __cpu_logical_map[NR_CPUS];
/* Mask of CPUs which are currently definitely operating coherently */
extern cpumask_t cpu_coherent_mask;
+extern unsigned int smp_max_threads __initdata;
+
extern asmlinkage void smp_bootstrap(void);
extern void calculate_cpu_foreign_map(void);
diff --git a/arch/mips/kernel/smp-cps.c b/arch/mips/kernel/smp-cps.c
index d7fdbec232da..474318bc08cb 100644
--- a/arch/mips/kernel/smp-cps.c
+++ b/arch/mips/kernel/smp-cps.c
@@ -25,24 +25,13 @@
#include <asm/time.h>
#include <asm/uasm.h>
-static bool threads_disabled;
static DECLARE_BITMAP(core_power, NR_CPUS);
struct core_boot_config *mips_cps_core_bootcfg;
-static int __init setup_nothreads(char *s)
-{
- threads_disabled = true;
- return 0;
-}
-early_param("nothreads", setup_nothreads);
-
static unsigned core_vpe_count(unsigned int cluster, unsigned core)
{
- if (threads_disabled)
- return 1;
-
- return mips_cps_numvps(cluster, core);
+ return min(smp_max_threads, mips_cps_numvps(cluster, core));
}
static void __init cps_smp_setup(void)
diff --git a/arch/mips/kernel/smp-mt.c b/arch/mips/kernel/smp-mt.c
index 5f04a0141068..7729cc733421 100644
--- a/arch/mips/kernel/smp-mt.c
+++ b/arch/mips/kernel/smp-mt.c
@@ -46,7 +46,8 @@ static void __init smvp_copy_vpe_config(void)
static unsigned int __init smvp_vpe_init(unsigned int tc, unsigned int mvpconf0,
unsigned int ncpu)
{
- if (tc > ((mvpconf0 & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT))
+ if (tc >= smp_max_threads ||
+ (tc > ((mvpconf0 & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT)))
return ncpu;
/* Deactivate all but VPE 0 */
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 90c71d800b59..8fbef537fb88 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -73,6 +73,24 @@ static cpumask_t cpu_core_setup_map;
cpumask_t cpu_coherent_mask;
+unsigned int smp_max_threads __initdata = UINT_MAX;
+
+static int __init early_nosmt(char *s)
+{
+ smp_max_threads = 1;
+ return 0;
+}
+early_param("nosmt", early_nosmt);
+
+static int __init early_smt(char *s)
+{
+ get_option(&s, &smp_max_threads);
+ /* Ensure at least one thread is available */
+ smp_max_threads = clamp_val(smp_max_threads, 1U, UINT_MAX);
+ return 0;
+}
+early_param("smt", early_smt);
+
#ifdef CONFIG_GENERIC_IRQ_IPI
static struct irq_desc *call_desc;
static struct irq_desc *sched_desc;
--
2.39.2 (Apple Git-143)
