MIPS: Rework smt cmdline parameters

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@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e5bab2..50439f4 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3838,7 +3838,7 @@
        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).
@@ -5735,7 +5735,7 @@
                                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 aab8981..a40d8c0 100644 (file)
--- 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 62f677b..bea6a13 100644 (file)
--- 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 5f04a01..7729cc7 100644 (file)
--- 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 1d93b85..280251e 100644 (file)
--- 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;