linux-kernel - Re: [PATCH v2 3/7] irqchip/gicv2m: Don't map the MSI page in gicv2m_compose_msi

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Message-ID: <c4013c08-3d32-769c-447b-38a0a0dcf152@redhat.com>
Date:   Tue, 30 Apr 2019 14:34:48 +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 3/7] irqchip/gicv2m: Don't map the MSI page in
 gicv2m_compose_msi_msg()

Hi Julien,

On 4/29/19 4:44 PM, Julien Grall wrote:
> gicv2m_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 GICv2m driver is reworked to avoid executing preemptible code in
> non-preemptible context. This can be achieved by preparing the MSI
> mapping when allocating the MSI interrupt.
> 
> Signed-off-by: Julien Grall <julien.grall@....com>
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric
> 
> ---
>     Changes in v2:
>         - Rework the commit message to use imperative mood
> ---
>  drivers/irqchip/irq-gic-v2m.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
> index f5fe0100f9ff..4359f0583377 100644
> --- a/drivers/irqchip/irq-gic-v2m.c
> +++ b/drivers/irqchip/irq-gic-v2m.c
> @@ -110,7 +110,7 @@ static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	if (v2m->flags & GICV2M_NEEDS_SPI_OFFSET)
>  		msg->data -= v2m->spi_offset;
>  
> -	iommu_dma_map_msi_msg(data->irq, msg);
> +	iommu_dma_compose_msi_msg(irq_data_get_msi_desc(data), msg);
>  }
>  
>  static struct irq_chip gicv2m_irq_chip = {
> @@ -167,6 +167,7 @@ static void gicv2m_unalloc_msi(struct v2m_data *v2m, unsigned int hwirq,
>  static int gicv2m_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>  				   unsigned int nr_irqs, void *args)
>  {
> +	msi_alloc_info_t *info = args;
>  	struct v2m_data *v2m = NULL, *tmp;
>  	int hwirq, offset, i, err = 0;
>  
> @@ -186,6 +187,11 @@ static int gicv2m_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>  
>  	hwirq = v2m->spi_start + offset;
>  
> +	err = iommu_dma_prepare_msi(info->desc,
> +				    v2m->res.start + V2M_MSI_SETSPI_NS);
> +	if (err)
> +		return err;
> +
>  	for (i = 0; i < nr_irqs; i++) {
>  		err = gicv2m_irq_gic_domain_alloc(domain, virq + i, hwirq + i);
>  		if (err)
>