virtio_ring: introduce dma map api for virtqueue

Added virtqueue_dma_map_api* to map DMA addresses for virtual memory in
advance. The purpose is to keep memory mapped across multiple add/get
buf operations.
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Message-Id: <20230810123057.43407-11-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_ring.c

@@ -3106,4 +3106,73 @@ const struct vring *virtqueue_get_vring(const struct virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(virtqueue_get_vring);
 
+/**
+ * virtqueue_dma_map_single_attrs - map DMA for _vq
+ * @_vq: the struct virtqueue we're talking about.
+ * @ptr: the pointer of the buffer to do dma
+ * @size: the size of the buffer 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_single_attrs(struct virtqueue *_vq, void *ptr,
+					  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_addr_t)virt_to_phys(ptr);
+
+	return dma_map_single_attrs(vring_dma_dev(vq), ptr, size, dir, attrs);
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_map_single_attrs);
+
+/**
+ * virtqueue_dma_unmap_single_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_single_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_single_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_single_attrs);
+
+/**
+ * virtqueue_dma_mapping_error - check dma address
+ * @_vq: the struct virtqueue we're talking about.
+ * @addr: DMA address
+ *
+ * Returns 0 means dma valid. Other means invalid dma address.
+ */
+int virtqueue_dma_mapping_error(struct virtqueue *_vq, dma_addr_t addr)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (!vq->use_dma_api)
+		return 0;
+
+	return dma_mapping_error(vring_dma_dev(vq), addr);
+}
+EXPORT_SYMBOL_GPL(virtqueue_dma_mapping_error);
+
 MODULE_LICENSE("GPL");

include/linux/virtio.h

@@ -9,6 +9,7 @@
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
 #include <linux/gfp.h>
+#include <linux/dma-mapping.h>
 
 /**
  * struct virtqueue - a queue to register buffers for sending or receiving.
@@ -212,4 +213,11 @@ void unregister_virtio_driver(struct virtio_driver *drv);
 #define module_virtio_driver(__virtio_driver) \
 	module_driver(__virtio_driver, register_virtio_driver, \
 			unregister_virtio_driver)
+
+dma_addr_t virtqueue_dma_map_single_attrs(struct virtqueue *_vq, void *ptr, size_t size,
+					  enum dma_data_direction dir, unsigned long attrs);
+void virtqueue_dma_unmap_single_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);
 #endif /* _LINUX_VIRTIO_H */