[RFC,v1,03/18] dma-mapping: check if IOVA can be used

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 43520e7275cc..89e34503e0bb 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -597,19 +597,6 @@  static int iova_reserve_iommu_regions(struct device *dev,
 	return ret;
 }
 
-static bool dev_is_untrusted(struct device *dev)
-{
-	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
-}
-
-static bool dev_use_swiotlb(struct device *dev, size_t size,
-			    enum dma_data_direction dir)
-{
-	return IS_ENABLED(CONFIG_SWIOTLB) &&
-		(dev_is_untrusted(dev) ||
-		 dma_kmalloc_needs_bounce(dev, size, dir));
-}
-
 static bool dev_use_sg_swiotlb(struct device *dev, struct scatterlist *sg,
 			       int nents, enum dma_data_direction dir)
 {
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 4f47a13cb500..6ceea32bb041 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -964,8 +964,8 @@  void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 
-static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
-						    struct device *dev)
+enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
+					     struct device *dev)
 {
 	enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
 	struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 23e5e2f63a1c..b52e9c8db241 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -9,6 +9,7 @@ 
 #include <linux/dma-mapping.h>
 #include <linux/pgtable.h>
 #include <linux/slab.h>
+#include <linux/pci.h>
 
 struct cma;
 struct iommu_ops;
@@ -348,6 +349,19 @@  static inline bool dma_kmalloc_needs_bounce(struct device *dev, size_t size,
 	return !dma_kmalloc_safe(dev, dir) && !dma_kmalloc_size_aligned(size);
 }
 
+static inline bool dev_is_untrusted(struct device *dev)
+{
+	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
+}
+
+static inline bool dev_use_swiotlb(struct device *dev, size_t size,
+				   enum dma_data_direction dir)
+{
+	return IS_ENABLED(CONFIG_SWIOTLB) &&
+	       (dev_is_untrusted(dev) ||
+		dma_kmalloc_needs_bounce(dev, size, dir));
+}
+
 void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp_t gfp, unsigned long attrs);
 void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,
@@ -514,6 +528,8 @@  struct pci_p2pdma_map_state {
 enum pci_p2pdma_map_type
 pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
 		       struct scatterlist *sg);
+enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
+					     struct device *dev);
 #else /* CONFIG_PCI_P2PDMA */
 static inline enum pci_p2pdma_map_type
 pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
@@ -521,6 +537,11 @@  pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
 {
 	return PCI_P2PDMA_MAP_NOT_SUPPORTED;
 }
+static inline enum pci_p2pdma_map_type
+pci_p2pdma_map_type(struct dev_pagemap *pgmap, struct device *dev)
+{
+	return PCI_P2PDMA_MAP_NOT_SUPPORTED;
+}
 #endif /* CONFIG_PCI_P2PDMA */
 
 #endif /* _LINUX_DMA_MAP_OPS_H */
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 673ddcf140ff..9d1e020869a6 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -100,6 +100,11 @@  struct dma_iova_attrs {
 	unsigned long attrs;
 };
 
+struct dma_iova_state {
+	struct dma_iova_attrs *iova;
+	struct dma_memory_type *type;
+};
+
 #ifdef CONFIG_DMA_API_DEBUG
 void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
 void debug_dma_map_single(struct device *dev, const void *addr,
@@ -178,6 +183,7 @@  int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
 		size_t size, struct sg_table *sgt);
 
 void dma_get_memory_type(struct page *page, struct dma_memory_type *type);
+bool dma_can_use_iova(struct dma_iova_state *state, size_t size);
 #else /* CONFIG_HAS_DMA */
 static inline int dma_alloc_iova(struct dma_iova_attrs *iova)
 {
@@ -319,6 +325,10 @@  static inline void dma_get_memory_type(struct page *page,
 				       struct dma_memory_type *type)
 {
 }
+static inline bool dma_can_use_iova(struct dma_iova_state *state, size_t size)
+{
+	return false;
+}
 #endif /* CONFIG_HAS_DMA */
 
 #if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 0c8f51010d08..9044ee525fdb 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -968,3 +968,35 @@  void dma_free_iova(struct dma_iova_attrs *iova)
 	ops->free_iova(dev, iova->addr, iova->size);
 }
 EXPORT_SYMBOL_GPL(dma_free_iova);
+
+/**
+ * dma_can_use_iova - check if the device type is valid
+ *                    and won't take SWIOTLB path
+ * @state: IOVA state
+ * @size: size of the buffer
+ *
+ * Return %true if the device should use swiotlb for the given buffer, else
+ * %false.
+ */
+bool dma_can_use_iova(struct dma_iova_state *state, size_t size)
+{
+	struct device *dev = state->iova->dev;
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+	struct dma_memory_type *type = state->type;
+	enum pci_p2pdma_map_type map;
+
+	if (is_swiotlb_force_bounce(dev) ||
+	    dev_use_swiotlb(dev, size, state->iova->dir))
+		return false;
+
+	if (dma_map_direct(dev, ops) || !ops->alloc_iova)
+		return false;
+
+	if (type->type == DMA_MEMORY_TYPE_P2P) {
+		map = pci_p2pdma_map_type(type->p2p_pgmap, dev);
+		return map == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
+	}
+
+	return type->type == DMA_MEMORY_TYPE_NORMAL;
+}
+EXPORT_SYMBOL_GPL(dma_can_use_iova);