Re: [PATCH v2 3/3] virtio_ring: Use const to annotate read-only pointer params

Feng Liu via Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx> · Thu, 30 Mar 2023 14:22:44 -0400

On 2023-03-16 p.m.11:17, Jason Wang wrote:
External email: Use caution opening links or attachments


On Thu, Mar 16, 2023 at 2:55 AM Feng Liu <feliu@xxxxxxxxxx> wrote:

Add const to make the read-only pointer parameters clear, similar to
many existing functions.

Use `container_of_const` to implement `to_vvq`, which ensures the
const-ness of read-only parameters and avoids accidental modification
of their members.

Signed-off-by: Feng Liu <feliu@xxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>

Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks

Hi Michael & Jason
        Could you please help to take these reviewed/acked patches forward?
Thanks so much



---
v0 -> v1
feedbacks from Michael S. Tsirkin
- use `container_of_const` to implement `to_vvq`
---
  drivers/virtio/virtio_ring.c | 36 ++++++++++++++++++------------------
  include/linux/virtio.h       | 14 +++++++-------
  2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a26fab91c59f..4c3bb0ddeb9b 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -231,9 +231,9 @@ static void vring_free(struct virtqueue *_vq);
   * Helpers.
   */

-#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
+#define to_vvq(_vq) container_of_const(_vq, struct vring_virtqueue, vq)

-static bool virtqueue_use_indirect(struct vring_virtqueue *vq,
+static bool virtqueue_use_indirect(const struct vring_virtqueue *vq,
                                    unsigned int total_sg)
  {
         /*
@@ -269,7 +269,7 @@ static bool virtqueue_use_indirect(struct vring_virtqueue *vq,
   * unconditionally on data path.
   */

-static bool vring_use_dma_api(struct virtio_device *vdev)
+static bool vring_use_dma_api(const struct virtio_device *vdev)
  {
         if (!virtio_has_dma_quirk(vdev))
                 return true;
@@ -289,7 +289,7 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
         return false;
  }

-size_t virtio_max_dma_size(struct virtio_device *vdev)
+size_t virtio_max_dma_size(const struct virtio_device *vdev)
  {
         size_t max_segment_size = SIZE_MAX;

@@ -423,7 +423,7 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
   */

  static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
-                                          struct vring_desc *desc)
+                                          const struct vring_desc *desc)
  {
         u16 flags;

@@ -1183,7 +1183,7 @@ static u16 packed_last_used(u16 last_used_idx)
  }

  static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
-                                    struct vring_desc_extra *extra)
+                                    const struct vring_desc_extra *extra)
  {
         u16 flags;

@@ -1206,7 +1206,7 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
  }

  static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
-                                  struct vring_packed_desc *desc)
+                                   const struct vring_packed_desc *desc)
  {
         u16 flags;

@@ -2786,10 +2786,10 @@ EXPORT_SYMBOL_GPL(vring_transport_features);
   * Returns the size of the vring.  This is mainly used for boasting to
   * userspace.  Unlike other operations, this need not be serialized.
   */
-unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
+unsigned int virtqueue_get_vring_size(const struct virtqueue *_vq)
  {

-       struct vring_virtqueue *vq = to_vvq(_vq);
+       const struct vring_virtqueue *vq = to_vvq(_vq);

         return vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num;
  }
@@ -2819,9 +2819,9 @@ void __virtqueue_unbreak(struct virtqueue *_vq)
  }
  EXPORT_SYMBOL_GPL(__virtqueue_unbreak);

-bool virtqueue_is_broken(struct virtqueue *_vq)
+bool virtqueue_is_broken(const struct virtqueue *_vq)
  {
-       struct vring_virtqueue *vq = to_vvq(_vq);
+       const struct vring_virtqueue *vq = to_vvq(_vq);

         return READ_ONCE(vq->broken);
  }
@@ -2868,9 +2868,9 @@ void __virtio_unbreak_device(struct virtio_device *dev)
  }
  EXPORT_SYMBOL_GPL(__virtio_unbreak_device);

-dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
+dma_addr_t virtqueue_get_desc_addr(const struct virtqueue *_vq)
  {
-       struct vring_virtqueue *vq = to_vvq(_vq);
+       const struct vring_virtqueue *vq = to_vvq(_vq);

         BUG_ON(!vq->we_own_ring);

@@ -2881,9 +2881,9 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
  }
  EXPORT_SYMBOL_GPL(virtqueue_get_desc_addr);

-dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
+dma_addr_t virtqueue_get_avail_addr(const struct virtqueue *_vq)
  {
-       struct vring_virtqueue *vq = to_vvq(_vq);
+       const struct vring_virtqueue *vq = to_vvq(_vq);

         BUG_ON(!vq->we_own_ring);

@@ -2895,9 +2895,9 @@ dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
  }
  EXPORT_SYMBOL_GPL(virtqueue_get_avail_addr);

-dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
+dma_addr_t virtqueue_get_used_addr(const struct virtqueue *_vq)
  {
-       struct vring_virtqueue *vq = to_vvq(_vq);
+       const struct vring_virtqueue *vq = to_vvq(_vq);

         BUG_ON(!vq->we_own_ring);

@@ -2910,7 +2910,7 @@ dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
  EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);

  /* Only available for split ring */
-const struct vring *virtqueue_get_vring(struct virtqueue *vq)
+const struct vring *virtqueue_get_vring(const struct virtqueue *vq)
  {
         return &to_vvq(vq)->split.vring;
  }
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 2b472514c49b..c4225653f949 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -84,14 +84,14 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *vq);

  void *virtqueue_detach_unused_buf(struct virtqueue *vq);

-unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
+unsigned int virtqueue_get_vring_size(const struct virtqueue *vq);

-bool virtqueue_is_broken(struct virtqueue *vq);
+bool virtqueue_is_broken(const struct virtqueue *vq);

-const struct vring *virtqueue_get_vring(struct virtqueue *vq);
-dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq);
-dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq);
-dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq);
+const struct vring *virtqueue_get_vring(const struct virtqueue *vq);
+dma_addr_t virtqueue_get_desc_addr(const struct virtqueue *vq);
+dma_addr_t virtqueue_get_avail_addr(const struct virtqueue *vq);
+dma_addr_t virtqueue_get_used_addr(const struct virtqueue *vq);

  int virtqueue_resize(struct virtqueue *vq, u32 num,
                      void (*recycle)(struct virtqueue *vq, void *buf));
@@ -147,7 +147,7 @@ int virtio_device_restore(struct virtio_device *dev);
  #endif
  void virtio_reset_device(struct virtio_device *dev);

-size_t virtio_max_dma_size(struct virtio_device *vdev);
+size_t virtio_max_dma_size(const struct virtio_device *vdev);

  #define virtio_device_for_each_vq(vdev, vq) \
         list_for_each_entry(vq, &vdev->vqs, list)
--
2.34.1


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