dma-mapping: implement DMA_ATTR_MMIO for dma_(un)map_page_attrs()

Make dma_map_page_attrs() and dma_map_page_attrs() respect
DMA_ATTR_MMIO.

DMA_ATR_MMIO makes the functions behave the same as
dma_(un)map_resource():
 - No swiotlb is possible
 - Legacy dma_ops arches use ops->map_resource()
 - No kmsan
 - No arch_dma_map_phys_direct()

The prior patches have made the internal functions called here
support DMA_ATTR_MMIO.

This is also preparation for turning dma_map_resource() into an inline
calling dma_map_phys(DMA_ATTR_MMIO) to consolidate the flows.

Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Leon Romanovsky <[email protected]>
Signed-off-by: Marek Szyprowski <[email protected]>
Link: https://lore.kernel.org/r/3660e2c78ea409d6c483a215858fb3af52cd0ed3.1757423202.git.leonro@nvidia.com

Author: rleon

kernel/dma/mapping.c

@@ -158,6 +158,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 	phys_addr_t phys = page_to_phys(page) + offset;
+	bool is_mmio = attrs & DMA_ATTR_MMIO;
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
@@ -166,14 +167,25 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_map_phys_direct(dev, phys + size))
+	    (!is_mmio && arch_dma_map_phys_direct(dev, phys + size)))
 		addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
-	else
+	else if (is_mmio) {
+		if (!ops->map_resource)
+			return DMA_MAPPING_ERROR;
+
+		addr = ops->map_resource(dev, phys, size, dir, attrs);
+	} else {
+		/*
+		 * The dma_ops API contract for ops->map_page() requires
+		 * kmappable memory, while ops->map_resource() does not.
+		 */
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
+	}
 
-	kmsan_handle_dma(phys, size, dir);
+	if (!is_mmio)
+		kmsan_handle_dma(phys, size, dir);
 	trace_dma_map_phys(dev, phys, addr, size, dir, attrs);
 	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
 
@@ -185,14 +197,18 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
+	bool is_mmio = attrs & DMA_ATTR_MMIO;
 
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_unmap_phys_direct(dev, addr + size))
+	    (!is_mmio && arch_dma_unmap_phys_direct(dev, addr + size)))
 		dma_direct_unmap_phys(dev, addr, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
-	else
+	else if (is_mmio) {
+		if (ops->unmap_resource)
+			ops->unmap_resource(dev, addr, size, dir, attrs);
+	} else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	trace_dma_unmap_phys(dev, addr, size, dir, attrs);
 	debug_dma_unmap_phys(dev, addr, size, dir);