[PATCH 2/9] iommu/dma-iommu: Add function to flush any cached not present IOTLB entries

[Tom Murphy <tmurphy@arista.com>]

Both the AMD and Intel drivers can cache not present IOTLB entries. To
convert these drivers to the dma-iommu api we need a generic way to
flush the NP cache. IOMMU drivers which have a NP cache can implement
the .flush_np_cache function in the iommu ops struct. I will implement
.flush_np_cache for both the Intel and AMD drivers in later patches.

The Intel np-cache is described here:
https://software.intel.com/sites/default/files/managed/c5/15/vt-directed-io-spec.pdf#G7.66452

And the AMD np-cache is described here:
https://developer.amd.com/wordpress/media/2012/10/34434-IOMMU-Rev_1.26_2-11-09.pdf#page=63

Signed-off-by: Tom Murphy <tmurphy@arista.com>
---
 drivers/iommu/dma-iommu.c | 10 ++++++++++
 include/linux/iommu.h     |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 1a4bff3f8427..cc5da30d6e58 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -594,6 +594,9 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
 			< size)
 		goto out_free_sg;
 
+	if (domain->ops->flush_np_cache)
+		domain->ops->flush_np_cache(domain, iova, size);
+
 	*handle = iova;
 	sg_free_table(&sgt);
 	return pages;
@@ -652,6 +655,10 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
 		iommu_dma_free_iova(cookie, iova, size);
 		return DMA_MAPPING_ERROR;
 	}
+
+	if (domain->ops->flush_np_cache)
+		domain->ops->flush_np_cache(domain, iova, size);
+
 	return iova + iova_off;
 }
 
@@ -812,6 +819,9 @@ int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
 	if (iommu_map_sg_atomic(domain, iova, sg, nents, prot) < iova_len)
 		goto out_free_iova;
 
+	if (domain->ops->flush_np_cache)
+		domain->ops->flush_np_cache(domain, iova, iova_len);
+
 	return __finalise_sg(dev, sg, nents, iova);
 
 out_free_iova:
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 75559918d9bd..47ff8d731d6a 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -173,6 +173,7 @@ struct iommu_resv_region {
  * @iotlb_sync_map: Sync mappings created recently using @map to the hardware
  * @iotlb_sync: Flush all queued ranges from the hardware TLBs and empty flush
  *            queue
+ * @flush_np_cache: Flush the non present entry cache
  * @iova_to_phys: translate iova to physical address
  * @add_device: add device to iommu grouping
  * @remove_device: remove device from iommu grouping
@@ -209,6 +210,8 @@ struct iommu_ops {
 				unsigned long iova, size_t size);
 	void (*iotlb_sync_map)(struct iommu_domain *domain);
 	void (*iotlb_sync)(struct iommu_domain *domain);
+	void (*flush_np_cache)(struct iommu_domain *domain,
+				unsigned long iova, size_t size);
 	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t iova);
 	int (*add_device)(struct device *dev);
 	void (*remove_device)(struct device *dev);
-- 
2.17.1