virtio_ring: constify virtqueue pointer for DMA helpers

This patch constifies the virtqueue pointer for DMA helpers.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20250821064641.5025-2-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>

Author: jasowang

drivers/virtio/virtio_ring.c

@@ -3149,12 +3149,12 @@ EXPORT_SYMBOL_GPL(virtqueue_get_vring);
  *
  * 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,
+dma_addr_t virtqueue_dma_map_single_attrs(const struct virtqueue *_vq, void *ptr,
 					  size_t size,
 					  enum dma_data_direction dir,
 					  unsigned long attrs)
 {
-	struct vring_virtqueue *vq = to_vvq(_vq);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api) {
 		kmsan_handle_dma(virt_to_page(ptr), offset_in_page(ptr), size, dir);
@@ -3176,11 +3176,12 @@ EXPORT_SYMBOL_GPL(virtqueue_dma_map_single_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,
+void virtqueue_dma_unmap_single_attrs(const 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);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api)
 		return;
@@ -3196,9 +3197,9 @@ EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_single_attrs);
  *
  * Returns 0 means dma valid. Other means invalid dma address.
  */
-int virtqueue_dma_mapping_error(struct virtqueue *_vq, dma_addr_t addr)
+int virtqueue_dma_mapping_error(const struct virtqueue *_vq, dma_addr_t addr)
 {
-	struct vring_virtqueue *vq = to_vvq(_vq);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api)
 		return 0;
@@ -3217,9 +3218,9 @@ EXPORT_SYMBOL_GPL(virtqueue_dma_mapping_error);
  *
  * return bool
  */
-bool virtqueue_dma_need_sync(struct virtqueue *_vq, dma_addr_t addr)
+bool virtqueue_dma_need_sync(const struct virtqueue *_vq, dma_addr_t addr)
 {
-	struct vring_virtqueue *vq = to_vvq(_vq);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api)
 		return false;
@@ -3240,12 +3241,12 @@ EXPORT_SYMBOL_GPL(virtqueue_dma_need_sync);
  * the DMA address really needs to be synchronized
  *
  */
-void virtqueue_dma_sync_single_range_for_cpu(struct virtqueue *_vq,
+void virtqueue_dma_sync_single_range_for_cpu(const struct virtqueue *_vq,
 					     dma_addr_t addr,
 					     unsigned long offset, size_t size,
 					     enum dma_data_direction dir)
 {
-	struct vring_virtqueue *vq = to_vvq(_vq);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 	struct device *dev = vring_dma_dev(vq);
 
 	if (!vq->use_dma_api)
@@ -3266,12 +3267,12 @@ EXPORT_SYMBOL_GPL(virtqueue_dma_sync_single_range_for_cpu);
  * Before calling this function, use virtqueue_dma_need_sync() to confirm that
  * the DMA address really needs to be synchronized
  */
-void virtqueue_dma_sync_single_range_for_device(struct virtqueue *_vq,
+void virtqueue_dma_sync_single_range_for_device(const struct virtqueue *_vq,
 						dma_addr_t addr,
 						unsigned long offset, size_t size,
 						enum dma_data_direction dir)
 {
-	struct vring_virtqueue *vq = to_vvq(_vq);
+	const struct vring_virtqueue *vq = to_vvq(_vq);
 	struct device *dev = vring_dma_dev(vq);
 
 	if (!vq->use_dma_api)

include/linux/virtio.h

@@ -262,18 +262,18 @@ void unregister_virtio_driver(struct virtio_driver *drv);
 	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,
+dma_addr_t virtqueue_dma_map_single_attrs(const 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,
+void virtqueue_dma_unmap_single_attrs(const 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);
+int virtqueue_dma_mapping_error(const struct virtqueue *_vq, dma_addr_t addr);
 
-bool virtqueue_dma_need_sync(struct virtqueue *_vq, dma_addr_t addr);
-void virtqueue_dma_sync_single_range_for_cpu(struct virtqueue *_vq, dma_addr_t addr,
+bool virtqueue_dma_need_sync(const struct virtqueue *_vq, dma_addr_t addr);
+void virtqueue_dma_sync_single_range_for_cpu(const struct virtqueue *_vq, dma_addr_t addr,
 					     unsigned long offset, size_t size,
 					     enum dma_data_direction dir);
-void virtqueue_dma_sync_single_range_for_device(struct virtqueue *_vq, dma_addr_t addr,
+void virtqueue_dma_sync_single_range_for_device(const struct virtqueue *_vq, dma_addr_t addr,
 						unsigned long offset, size_t size,
 						enum dma_data_direction dir);