iommu/dma: Add support for mapping MSIs

When an MSI doorbell is located downstream of an IOMMU, attaching
devices to a DMA ops domain and switching on translation leads to a rude
shock when their attempt to write to the physical address returned by
the irqchip driver faults (or worse, writes into some already-mapped
buffer) and no interrupt is forthcoming.

Address this by adding a hook for relevant irqchip drivers to call from
their compose_msi_msg() callback, to swizzle the physical address with
an appropriatly-mapped IOVA for any device attached to one of our DMA
ops domains.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 81c5c8d167ad..5ee806e41b5c 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -21,6 +21,7 @@
 
 #ifdef CONFIG_IOMMU_DMA
 #include <linux/iommu.h>
+#include <linux/msi.h>
 
 int iommu_dma_init(void);
 
@@ -62,9 +63,13 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 int iommu_dma_supported(struct device *dev, u64 mask);
 int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
 
+/* The DMA API isn't _quite_ the whole story, though... */
+void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg);
+
 #else
 
 struct iommu_domain;
+struct msi_msg;
 
 static inline int iommu_dma_init(void)
 {
@@ -80,6 +85,10 @@ static inline void iommu_put_dma_cookie(struct iommu_domain *domain)
 {
 }
 
+static inline void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
+{
+}
+
 #endif	/* CONFIG_IOMMU_DMA */
 #endif	/* __KERNEL__ */
 #endif	/* __DMA_IOMMU_H */