linux-kernel - Re: [PATCH] irqchip/gic: Only allow the primary GIC to set the CPU map

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Date:	Thu, 30 Jul 2015 16:05:13 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Marc Zyngier <marc.zyngier@....com>,
	Russell King <linux@....linux.org.uk>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Jason Cooper" <jason@...edaemon.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] irqchip/gic: Only allow the primary GIC to set the CPU
 map


On 30/07/15 15:33, Marc Zyngier wrote:
> On 30/07/15 15:11, Jon Hunter wrote:
>> The gic_init_bases() function initialises an array that stores the mapping
>> between the GIC and CPUs. This array is a global array that is
>> unconditionally initialised on every call to gic_init_bases(). Although,
>> it is not common for there to be more than one GIC instance, there are
>> some devices that do support nested GIC controllers and gic_init_bases()
>> can be called more than once.
>>
>> A 2nd call to gic_init_bases() will clear the previous CPU mapping and
>> will only setup the mapping again for the CPU calling gic_init_bases().
>> Fix this by only allowing the CPU map to be configured for the primary GIC.
>>
>> For secondary GICs the CPU map is not relevant because these GICs do not
>> directly route the interrupts to the main CPU(s) but to other GICs or
>> devices.
>>
>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>> ---
>> This is a follow-up to the patch titled "irqchip: gic: Add a cpu map for
>> each GIC instance" and discussed here [1]. Based upon the discussion I have
>> re-worked and re-titled it approriately.
>>
>> [1] http://www.spinics.net/lists/kernel/msg2044421.html
>>
>>  drivers/irqchip/irq-gic.c | 43 +++++++++++++++++++++++++------------------
>>  1 file changed, 25 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
>> index a530d9a9b810..7566fe259d27 100644
>> --- a/drivers/irqchip/irq-gic.c
>> +++ b/drivers/irqchip/irq-gic.c
>> @@ -416,19 +416,26 @@ static void gic_cpu_init(struct gic_chip_data *gic)
>>  	int i;
>>  
>>  	/*
>> -	 * Get what the GIC says our CPU mask is.
>> +	 * Setting up the CPU map is only relevant for the primary GIC
>> +	 * because any nested/secondary GICs do not directly interface
>> +	 * with the CPU(s).
>>  	 */
>> -	BUG_ON(cpu >= NR_GIC_CPU_IF);
>> -	cpu_mask = gic_get_cpumask(gic);
>> -	gic_cpu_map[cpu] = cpu_mask;
>> +	if (gic == &gic_data[0]) {
>> +		/*
>> +		 * Get what the GIC says our CPU mask is.
>> +		 */
>> +		BUG_ON(cpu >= NR_GIC_CPU_IF);
>> +		cpu_mask = gic_get_cpumask(gic);
>> +		gic_cpu_map[cpu] = cpu_mask;
>>  
>> -	/*
>> -	 * Clear our mask from the other map entries in case they're
>> -	 * still undefined.
>> -	 */
>> -	for (i = 0; i < NR_GIC_CPU_IF; i++)
>> -		if (i != cpu)
>> -			gic_cpu_map[i] &= ~cpu_mask;
>> +		/*
>> +		 * Clear our mask from the other map entries in case they're
>> +		 * still undefined.
>> +		 */
>> +		for (i = 0; i < NR_GIC_CPU_IF; i++)
>> +			if (i != cpu)
>> +				gic_cpu_map[i] &= ~cpu_mask;
>> +	}
>>  
>>  	gic_cpu_config(dist_base, NULL);
>>  
>> @@ -977,13 +984,6 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
>>  	}
>>  
>>  	/*
>> -	 * Initialize the CPU interface map to all CPUs.
>> -	 * It will be refined as each CPU probes its ID.
>> -	 */
>> -	for (i = 0; i < NR_GIC_CPU_IF; i++)
>> -		gic_cpu_map[i] = 0xff;
>> -
>> -	/*
>>  	 * Find out how many interrupts are supported.
>>  	 * The GIC only supports up to 1020 interrupt sources.
>>  	 */
>> @@ -1028,6 +1028,13 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
>>  		return;
>>  
>>  	if (gic_nr == 0) {
>> +		/*
>> +		 * Initialize the CPU interface map to all CPUs.
>> +		 * It will be refined as each CPU probes its ID.
>> +		 * This is only necessary for the primary GIC.
>> +		 */
>> +		for (i = 0; i < NR_GIC_CPU_IF; i++)
>> +			gic_cpu_map[i] = 0xff;
>>  #ifdef CONFIG_SMP
>>  		set_smp_cross_call(gic_raise_softirq);
>>  		register_cpu_notifier(&gic_cpu_notifier);
>>
> 
> Looks good.
> 
> I think there is a another bug caused by 322895062 ("irqchip: gic:
> Preserve gic V2 bypass bits in cpu ctrl register"), where
> gic_cpu_if_up() only acts on the primary GIC. In the secondary GIC case,
> it will stay disabled.
> 
> Mind fixing this while you're at it?

Ah yes, I see. Ok, I will resend this with the other fix as a series.

Jon
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