arm64: Support hard limit of cpu count by nr_cpus

Enable the hard limit of cpu count by nr_cpus on arm64. The code is borrowed from MIPS.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---
 arch/arm64/kernel/setup.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

arch/arm64/kernel/setup.c +4 -0

index 536dce2..597b777 100644
@@ -224,6 +224,21 @@ static void __init request_standard_resources(void)
 
 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
 
+static void __init prefill_possible_map(void)
+{
+	int i, possible = num_possible_cpus();
+

Quoted 26 lines · Kefeng Wang

Enable the hard limit of cpu count by nr_cpus on arm64. The code is borrowed from MIPS.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---
 arch/arm64/kernel/setup.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

arch/arm64/kernel/setup.c +9 -0

index 536dce2..597b777 100644
@@ -224,6 +224,21 @@ static void __init request_standard_resources(void)
 
 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
 
+static void __init prefill_possible_map(void)
+{
+	int i, possible = num_possible_cpus();
+
+	if (possible > nr_cpu_ids)
+		possible = nr_cpu_ids;
+
+	for (i = 0; i < possible; i++)
+		set_cpu_possible(i, true);

arch/arm64/kernel/setup.c static void __init request_standard_resources(void) · line 240

Quoted 5 lines

arch/arm64/kernel/setup.c +5 -0

+	for (; i < NR_CPUS; i++)
+		set_cpu_possible(i, false);
+
+	nr_cpu_ids = possible;
+}

Shouldn't we just avoid marking those CPUs as possible in smp_cpu_setup, rather than rewriting things later on?

From 0965eebecbc5aea0473df0cb45d32b2fccf72a9a Mon Sep 17 00:00:00 2001

Also, can you explain exactly what functionality is missing at the moment, please? I assume it's the nr_cpus= option not working correctly?

Will

.

Quoted 27 lines · Will Deacon

Quoted 26 lines · Kefeng Wang

Enable the hard limit of cpu count by nr_cpus on arm64. The code is borrowed from MIPS.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---
 arch/arm64/kernel/setup.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

arch/arm64/kernel/setup.c +9 -0

index 536dce2..597b777 100644
@@ -224,6 +224,21 @@ static void __init request_standard_resources(void)
 
 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
 
+static void __init prefill_possible_map(void)
+{
+	int i, possible = num_possible_cpus();
+
+	if (possible > nr_cpu_ids)
+		possible = nr_cpu_ids;
+
+	for (i = 0; i < possible; i++)
+		set_cpu_possible(i, true);

Quoted 8 lines

arch/arm64/kernel/setup.c static void __init request_standard_resources(void) · line 240

Quoted 5 lines

arch/arm64/kernel/setup.c +5 -0

+	for (; i < NR_CPUS; i++)
+		set_cpu_possible(i, false);
+
+	nr_cpu_ids = possible;
+}

Shouldn't we just avoid marking those CPUs as possible in smp_cpu_setup, rather than rewriting things later on?

How about this one,

From 0965eebecbc5aea0473df0cb45d32b2fccf72a9a Mon Sep 17 00:00:00 2001
From: Kefeng Wang <[email protected]>
Date: Fri, 5 Aug 2016 17:44:33 +0800
Subject: [PATCH v2] arm64: Support hard limit of cpu count by nr_cpus

Enable the hard limit of cpu count by set boot options nr_cpus=x on arm64.

Signed-off-by Kefeng Wang <[email protected]>

---
 arch/arm64/kernel/smp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

arch/arm64/kernel/smp.c +0 -0

index 76a6d92..0ac3ff5 100644
@@ -496,7 +496,10 @@ static int __init smp_cpu_setup(int cpu)
 	if (cpu_ops[cpu]->cpu_init(cpu))

Quoted 7 lines · Kefeng Wang

Quoted 4 lines · Will Deacon

Quoted 3 lines · Kefeng Wang

Enable the hard limit of cpu count by nr_cpus on arm64. The code is borrowed from MIPS.

Or is this even better ?

arch/arm64/kernel/smp.c +2 -2

-                       cpu_count, NR_CPUS);
+                       cpu_count, nr_cpu_ids);
 
        if (!bootcpu_valid) {
                pr_err("missing boot CPU MPIDR, not enabling secondaries\n");

@@ -675,7 +675,7 @@ void __init smp_init_cpus(void)
         * with entries in cpu_logical_map while initializing the cpus.
         * If the cpu set-up fails, invalidate the cpu_logical_map entry.
         */
-       for (i = 1; i < NR_CPUS; i++) {
+       for (i = 1; i < nr_cpu_ids; i++) {
                if (cpu_logical_map(i) != INVALID_HWID) {
                        if (smp_cpu_setup(i))
                                cpu_logical_map(i) = INVALID_HWID;

Cheers
Suzuki

.

Enable the hard limit of cpu count by set boot options nr_cpus=x on arm64, and show a better warning when cpu number exceeds the limit.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---

Changed since v1:
- clip cpu number in smp_init_cpus suggested-by Will and Suzuki, and update the warning.

 arch/arm64/kernel/smp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

arch/arm64/kernel/smp.c +0 -0

index 76a6d92..cbfc31c 100644

Quoted 22 lines · Kefeng Wang

Enable the hard limit of cpu count by set boot options nr_cpus=x on arm64, and show a better warning when cpu number exceeds the limit.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---

Changed since v1:
- clip cpu number in smp_init_cpus suggested-by Will and Suzuki, and update the warning.

 arch/arm64/kernel/smp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

arch/arm64/kernel/smp.c +0 -0

index 76a6d92..cbfc31c 100644
@@ -661,9 +661,9 @@ void __init smp_init_cpus(void)
         acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
                       acpi_parse_gic_cpu_interface, 0);
 

arch/arm64/kernel/smp.c void __init smp_init_cpus(void) · line 666

Quoted 6 lines

arch/arm64/kernel/smp.c +3 -3

-    if (cpu_count > NR_CPUS)
-        pr_warn("no. of cores (%d) greater than configured maximum of %d - clipping\n",
-            cpu_count, NR_CPUS);
+    if (cpu_count > nr_cpu_ids)
+        pr_warn("%d cores exceeds configured maximum of %d - clipping\n",
+            cpu_count, nr_cpu_ids);

I think we should leave the message as it was, and is better than what you have changed it to.

With that change,

Reviewed-by Suzuki K Poulose <[email protected]>

.

Quoted 23 lines · Suzuki K Poulose

Quoted 22 lines · Kefeng Wang

Enable the hard limit of cpu count by set boot options nr_cpus=x on arm64, and show a better warning when cpu number exceeds the limit.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---

Changed since v1:
- clip cpu number in smp_init_cpus suggested-by Will and Suzuki, and update the warning.

 arch/arm64/kernel/smp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

arch/arm64/kernel/smp.c +0 -0

index 76a6d92..cbfc31c 100644
@@ -661,9 +661,9 @@ void __init smp_init_cpus(void)
         acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
                       acpi_parse_gic_cpu_interface, 0);
 

Quoted 9 lines

arch/arm64/kernel/smp.c void __init smp_init_cpus(void) · line 666

Quoted 6 lines

arch/arm64/kernel/smp.c +3 -3

-    if (cpu_count > NR_CPUS)
-        pr_warn("no. of cores (%d) greater than configured maximum of %d - clipping\n",
-            cpu_count, NR_CPUS);
+    if (cpu_count > nr_cpu_ids)
+        pr_warn("%d cores exceeds configured maximum of %d - clipping\n",
+            cpu_count, nr_cpu_ids);

I think we should leave the message as it was, and is better than what you have changed it to.

The old message is OF only and the old logic shows message when the first cpu number greater than NR_CPUS.

But now the cpu_count is the total cpu counts(get from DT or ACPI), so I change the message.

Quoted 9 lines

With that change,

Reviewed-by Suzuki K Poulose <[email protected]>

.

Quoted 36 lines · Kefeng Wang

Quoted 32 lines · Suzuki K Poulose

Quoted 19 lines · Kefeng Wang

Enable the hard limit of cpu count by set boot options nr_cpus=x on arm64, and show a better warning when cpu number exceeds the limit.

Reported-by Shiyuan Hu <[email protected]>

Signed-off-by Kefeng Wang <[email protected]>

---

Changed since v1:
- clip cpu number in smp_init_cpus suggested-by Will and Suzuki, and update the warning.

 arch/arm64/kernel/smp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

arch/arm64/kernel/smp.c +0 -0

index 76a6d92..cbfc31c 100644

arch/arm64/kernel/smp.c void __init smp_init_cpus(void) · line 666

Quoted 9 lines

arch/arm64/kernel/smp.c +3 -3

@@ -661,9 +661,9 @@ void __init smp_init_cpus(void)
         acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
                       acpi_parse_gic_cpu_interface, 0);
 
-    if (cpu_count > NR_CPUS)
-        pr_warn("no. of cores (%d) greater than configured maximum of %d - clipping\n",
-            cpu_count, NR_CPUS);
+    if (cpu_count > nr_cpu_ids)
+        pr_warn("%d cores exceeds configured maximum of %d - clipping\n",
+            cpu_count, nr_cpu_ids);

I think we should leave the message as it was, and is better than what you have changed it to.

Quoted 1 line

The old message is OF only and the old logic shows message when the first cpu number greater than NR_CPUS.

I think you misunderstood "of" (as in plain english) with OF (as in Open Firmware). To avoid the confusion, how about making it :

"Number of cores (%d) exceeds configured maximum of %d - clipping\n" ?

Certainly a message like :

"5 cores exceeds configured maximum of %d..." doesn't look nice.

Suzuki

Quoted 13 lines

But now the cpu_count is the total cpu counts(get from DT or ACPI), so I change the message.

Quoted 9 lines

With that change,

Reviewed-by Suzuki K Poulose <[email protected]>

.

.