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:   Tue, 30 Apr 2019 14:34:51 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Julien Grall <julien.grall@....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()

Hi Julien,

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?
> +
>  	for (i = 0; i < nr_irqs; i++) {
>  		err = its_irq_gic_domain_alloc(domain, virq + i, hwirq + i);
>  		if (err)
> 
Besides
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric