linux-kernel - Re: [PATCH] mips: smp-bmips: fix CPU mappings

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Message-Id: <5B471DA5-E911-4B7F-BD9A-CE2901C427FC@gmail.com>
Date:   Wed, 24 Feb 2021 08:07:57 +0100
From:   Álvaro Fernández Rojas <noltari@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Jonas Gorski <jonas.gorski@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mips: smp-bmips: fix CPU mappings

Hi Florian,

> El 24 feb 2021, a las 4:45, Florian Fainelli <f.fainelli@...il.com> escribió:
> 
> 
> 
> On 2/23/2021 4:48 AM, Álvaro Fernández Rojas wrote:
>> When booting bmips with SMP enabled on a BCM6358 running on CPU #1 instead of
>> CPU #0, the current CPU mapping code produces the following:
>> - smp_processor_id(): 0
>> - cpu_logical_map(): 1
>> - cpu_number_map(): 1
>> 
>> This is because SMP isn't supported on BCM6358 since it has a shared TLB, so
>> it is disabled and max_cpus is decreased from 2 to 1.
>> 
>> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
>> ---
>> arch/mips/kernel/smp-bmips.c | 27 +++++++++++++++++----------
>> 1 file changed, 17 insertions(+), 10 deletions(-)
>> 
>> diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
>> index 359b176b665f..c4760cb48a67 100644
>> --- a/arch/mips/kernel/smp-bmips.c
>> +++ b/arch/mips/kernel/smp-bmips.c
>> @@ -134,17 +134,24 @@ static void __init bmips_smp_setup(void)
>> 	if (!board_ebase_setup)
>> 		board_ebase_setup = &bmips_ebase_setup;
>> 
>> -	__cpu_number_map[boot_cpu] = 0;
>> -	__cpu_logical_map[0] = boot_cpu;
>> -
>> -	for (i = 0; i < max_cpus; i++) {
>> -		if (i != boot_cpu) {
>> -			__cpu_number_map[i] = cpu;
>> -			__cpu_logical_map[cpu] = i;
>> -			cpu++;
>> +	if (max_cpus > 1) {
>> +		__cpu_number_map[boot_cpu] = 0;
>> +		__cpu_logical_map[0] = boot_cpu;
>> +
>> +		for (i = 0; i < max_cpus; i++) {
>> +			if (i != boot_cpu) {
>> +				__cpu_number_map[i] = cpu;
>> +				__cpu_logical_map[cpu] = i;
>> +				cpu++;
>> +			}
>> +			set_cpu_possible(i, 1);
>> +			set_cpu_present(i, 1);
>> 		}
>> -		set_cpu_possible(i, 1);
>> -		set_cpu_present(i, 1);
>> +	} else {
>> +		__cpu_number_map[0] = boot_cpu;
>> +		__cpu_logical_map[0] = 0;
>> +		set_cpu_possible(0, 1);
>> +		set_cpu_possible(0, 1);
> 
> Duplicate line, with that fixed:

Nice catch, it should be set_cpu_present().

> 
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> -- 
> Florian