diff mbox

arm64: Support hard limit of cpu count by nr_cpus

Message ID e2f3ee03-24e7-fd28-4172-ff0c87f9f539@huawei.com
State New
Headers show

Commit Message

Kefeng Wang Aug. 5, 2016, 9:58 a.m. UTC 
On 2016/8/5 16:32, Will Deacon wrote:
> On Fri, Aug 05, 2016 at 02:03:55PM +0800, Kefeng Wang wrote:

>> Enable the hard limit of cpu count by nr_cpus on arm64.

>> The code is borrowed from MIPS.

>>

>> Reported-by: Shiyuan Hu <hushiyuan@huawei.com>

>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

>> ---

>>  arch/arm64/kernel/setup.c | 16 ++++++++++++++++

>>  1 file changed, 16 insertions(+)

>>

>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c

>> index 536dce2..597b777 100644

>> --- a/arch/arm64/kernel/setup.c

>> +++ b/arch/arm64/kernel/setup.c

>> @@ -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);

>> +	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 <wangkefeng.wang@huawei.com>

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 <wangkefeng.wang@huawei.com>

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

-- 
1.7.12.4


> 

> Also, can you explain exactly what functionality is missing at the moment,

> please? I assume it's the nr_cpus= option not working correctly?


Yes. they use same bootargs nr_cpus=1 on both arm64 and x86, but find it can't work in arm64.

> 

> Will

> 

> .

> 



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Comments

Kefeng Wang Aug. 8, 2016, 5:29 a.m. UTC | #1 
On 2016/8/5 18:19, Suzuki K Poulose wrote:
> On 05/08/16 10:58, Kefeng Wang wrote:

>>

>>

>> On 2016/8/5 16:32, Will Deacon wrote:

>>> On Fri, Aug 05, 2016 at 02:03:55PM +0800, Kefeng Wang wrote:

>>>> Enable the hard limit of cpu count by nr_cpus on arm64.

>>>> The code is borrowed from MIPS.

>>>>

[...]
> 

> Or is this even better ?


Agree, and let's show a better warning.

> 

> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c

> index 490db85..dbd6a5e 100644

> --- a/arch/arm64/kernel/smp.c

> +++ b/arch/arm64/kernel/smp.c

> @@ -659,9 +659,9 @@ 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)

> +       if (cpu_count > nr_cpu_ids)

>                 pr_warn("no. of cores (%d) greater than configured maximum of %d - clipping\n",


  change to 	  pr_warn("%d cores exceeds configured maximum of %d - clipping\n",

Thanks,
Kefeng

> -                       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

> 

> .

> 



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diff mbox

Patch

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 76a6d92..0ac3ff5 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -496,7 +496,10 @@  static int __init smp_cpu_setup(int cpu)
 	if (cpu_ops[cpu]->cpu_init(cpu))
 		return -ENODEV;

-	set_cpu_possible(cpu, true);
+	if (cpu < nr_cpu_ids)
+		set_cpu_possible(cpu, true);
+	else
+		return -EINVAL;

 	return 0;
 }