irqchip/gicv2m: Don't map the MSI page in gicv2m_compose_msi_msg()

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@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

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)