linux-kernel - Re: [PATCH V5 1/9] virtio_ring: constify virtqueue pointer for DMA helpers

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Message-ID: <20250921165434-mutt-send-email-mst@kernel.org>
Date: Sun, 21 Sep 2025 16:55:07 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
	hch@...radead.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH V5 1/9] virtio_ring: constify virtqueue pointer for DMA
 helpers

On Wed, Aug 13, 2025 at 01:48:23PM +0800, Jason Wang wrote:
> This patch consities virtqueue point for DMA helpers.

constifies the virtqueue pointer

> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/virtio/virtio_ring.c | 25 +++++++++++++------------
>  include/linux/virtio.h       | 12 ++++++------
>  2 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index f5062061c408..103bad8cffff 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/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)
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 8b745ce0cf5f..cf8def717dfd 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -259,18 +259,18 @@ 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);
>  
> -- 
> 2.31.1