[PATCH vhost 14/17] virtio_ring: introduce dma map api for page

[Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>]

The virtio-net sq will use these APIs to map the scatterlist.
For scatterlist, the page dma APIs are more appropriate.

dma_addr_t virtqueue_dma_map_page_attrs(struct virtqueue *_vq, struct page *page,
                                       size_t offset, size_t size,
                                       enum dma_data_direction dir,
                                       unsigned long attrs);
void virtqueue_dma_unmap_page_attrs(struct virtqueue *_vq, dma_addr_t addr,
                                   size_t size, enum dma_data_direction dir,
                                   unsigned long attrs);

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 52 ++++++++++++++++++++++++++++++++++++
 include/linux/virtio.h       |  7 +++++
 2 files changed, 59 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index ccdd6dd3062f..47aa31ce69e7 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -3117,6 +3117,58 @@ void virtqueue_dma_unmap_single_attrs(struct virtqueue *_vq, dma_addr_t addr,
 }
 EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_single_attrs);
 
+/**
+ * virtqueue_dma_map_page_attrs - map DMA for _vq
+ * @_vq: the struct virtqueue we're talking about.
+ * @page: the page to do dma
+ * @offset: the offset inside the page
+ * @size: the size of the page to do dma
+ * @dir: DMA direction
+ * @attrs: DMA Attrs
+ *
+ * The caller calls this to do dma mapping in advance. The DMA address can be
+ * passed to this _vq when it is in pre-mapped mode.
+ *
+ * return DMA address. Caller should check that by virtqueue_dma_mapping_error().
+ */
+dma_addr_t virtqueue_dma_map_page_attrs(struct virtqueue *_vq, struct page *page,
+					size_t offset, size_t size,
+					enum dma_data_direction dir,
+					unsigned long attrs)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (!vq->use_dma_api)
+		return page_to_phys(page) + offset;
+
+	return dma_map_page_attrs(vring_dma_dev(vq), page, offset, size, dir, attrs);
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_map_page_attrs);
+
+/**
+ * virtqueue_dma_unmap_page_attrs - unmap DMA for _vq
+ * @_vq: the struct virtqueue we're talking about.
+ * @addr: the dma address to unmap
+ * @size: the size of the buffer
+ * @dir: DMA direction
+ * @attrs: DMA Attrs
+ *
+ * Unmap the address that is mapped by the virtqueue_dma_map_* APIs.
+ *
+ */
+void virtqueue_dma_unmap_page_attrs(struct virtqueue *_vq, dma_addr_t addr,
+				    size_t size, enum dma_data_direction dir,
+				    unsigned long attrs)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (!vq->use_dma_api)
+		return;
+
+	dma_unmap_page_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_page_attrs);
+
 /**
  * virtqueue_dma_mapping_error - check dma address
  * @_vq: the struct virtqueue we're talking about.
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 7f16bacc6c49..8a8d282982ad 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -216,6 +216,13 @@ dma_addr_t virtqueue_dma_map_single_attrs(struct virtqueue *_vq, void *ptr, size
 void virtqueue_dma_unmap_single_attrs(struct virtqueue *_vq, dma_addr_t addr,
 				      size_t size, enum dma_data_direction dir,
 				      unsigned long attrs);
+dma_addr_t virtqueue_dma_map_page_attrs(struct virtqueue *_vq, struct page *page,
+					size_t offset, size_t size,
+					enum dma_data_direction dir,
+					unsigned long attrs);
+void virtqueue_dma_unmap_page_attrs(struct virtqueue *_vq, dma_addr_t addr,
+				    size_t size, enum dma_data_direction dir,
+				    unsigned long attrs);
 int virtqueue_dma_mapping_error(struct virtqueue *_vq, dma_addr_t addr);
 
 bool virtqueue_dma_need_sync(struct virtqueue *_vq, dma_addr_t addr);
-- 
2.32.0.3.g01195cf9f