linux-kernel - Re: [PATCH v2 4/7] irqchip/gic-v3-its: Don't map the MSI page in its_irq_compose_msi

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Date:   Wed, 1 May 2019 12:14:29 +0100
From:   Julien Grall <julien.grall@....com>
To:     Auger Eric <eric.auger@...hat.com>, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org
Cc:     jason@...edaemon.net, douliyangs@...il.com, marc.zyngier@....com,
        robin.murphy@....com, miquel.raynal@...tlin.com,
        tglx@...utronix.de, logang@...tatee.com, bigeasy@...utronix.de,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v2 4/7] irqchip/gic-v3-its: Don't map the MSI page in
 its_irq_compose_msi_msg()

On 30/04/2019 13:34, Auger Eric wrote:
> Hi Julien,

Hi Eric,

Thank you for the review!

> 
> On 4/29/19 4:44 PM, Julien Grall wrote:
>> its_irq_compose_msi_msg() may be called from non-preemptible context.
>> However, on RT, iommu_dma_map_msi_msg requires to be called from a
>> preemptible context.
>>
>> A recent change split iommu_dma_map_msi_msg() in two new functions:
>> one that should be called in preemptible context, the other does
>> not have any requirement.
>>
>> The GICv3 ITS driver is reworked to avoid executing preemptible code in
>> non-preemptible context. This can be achieved by preparing the MSI
>> maping when allocating the MSI interrupt.
> mapping
>>
>> Signed-off-by: Julien Grall <julien.grall@....com>
>>
>> ---
>>      Changes in v2:
>>          - Rework the commit message to use imperative mood
>> ---
>>   drivers/irqchip/irq-gic-v3-its.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
>> index 7577755bdcf4..12ddbcfe1b1e 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -1179,7 +1179,7 @@ static void its_irq_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
>>   	msg->address_hi		= upper_32_bits(addr);
>>   	msg->data		= its_get_event_id(d);
>>   
>> -	iommu_dma_map_msi_msg(d->irq, msg);
>> +	iommu_dma_compose_msi_msg(irq_data_get_msi_desc(d), msg);
>>   }
>>   
>>   static int its_irq_set_irqchip_state(struct irq_data *d,
>> @@ -2566,6 +2566,7 @@ static int its_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>>   {
>>   	msi_alloc_info_t *info = args;
>>   	struct its_device *its_dev = info->scratchpad[0].ptr;
>> +	struct its_node *its = its_dev->its;
>>   	irq_hw_number_t hwirq;
>>   	int err;
>>   	int i;
>> @@ -2574,6 +2575,8 @@ static int its_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>>   	if (err)
>>   		return err;
>>   
>> +	err = iommu_dma_prepare_msi(info->desc, its->get_msi_base(its_dev));
> Test err as in gicv2m driver?

Hmmm yes. Marc, do you want me to respin the patch?

Cheers,

-- 
Julien Grall