genirq/msi: Add a new field in msi_desc to store an IOMMU cookie

When an MSI doorbell is located downstream of an IOMMU, it is required
to swizzle the physical address with an appropriately-mapped IOVA for any
device attached to one of our DMA ops domain.

At the moment, the allocation of the mapping may be done when composing
the message. However, the composing may be done in non-preemtible
context while the allocation requires to be called from preemptible
context.

A follow-up change will split the current logic in two functions
requiring to keep an IOMMU cookie per MSI.

A new field is introduced in msi_desc to store an IOMMU cookie. As the
cookie may not be required in some configuration, the field is protected
under a new config CONFIG_IRQ_MSI_IOMMU.

A pair of helpers has also been introduced to access the field.
Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

include/linux/msi.h

@@ -86,6 +86,9 @@ struct msi_desc {
 	struct device			*dev;
 	struct msi_msg			msg;
 	struct irq_affinity_desc	*affinity;
+#ifdef CONFIG_IRQ_MSI_IOMMU
+	const void			*iommu_cookie;
+#endif
 
 	union {
 		/* PCI MSI/X specific data */
@@ -129,6 +132,29 @@ struct msi_desc {
 #define for_each_msi_entry_safe(desc, tmp, dev)	\
 	list_for_each_entry_safe((desc), (tmp), dev_to_msi_list((dev)), list)
 
+#ifdef CONFIG_IRQ_MSI_IOMMU
+static inline const void *msi_desc_get_iommu_cookie(struct msi_desc *desc)
+{
+	return desc->iommu_cookie;
+}
+
+static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
+					     const void *iommu_cookie)
+{
+	desc->iommu_cookie = iommu_cookie;
+}
+#else
+static inline const void *msi_desc_get_iommu_cookie(struct msi_desc *desc)
+{
+	return NULL;
+}
+
+static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
+					     const void *iommu_cookie)
+{
+}
+#endif
+
 #ifdef CONFIG_PCI_MSI
 #define first_pci_msi_entry(pdev)	first_msi_entry(&(pdev)->dev)
 #define for_each_pci_msi_entry(desc, pdev)	\

kernel/irq/Kconfig

@@ -91,6 +91,9 @@ config GENERIC_MSI_IRQ_DOMAIN
 	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_MSI_IRQ
 
+config IRQ_MSI_IOMMU
+	bool
+
 config HANDLE_DOMAIN_IRQ
 	bool