Linux Virtualization - Mar 2023 - [PATCH v2 3/3] virtio_ring: Use const to annotate read-only pointer params

On Thu, Mar 16, 2023 at 2:55?AM Feng Liu <feliu at nvidia.com>
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 at nvidia.com>
> Reviewed-by: Jiri Pirko <jiri at nvidia.com>
Acked-by: Jason Wang <jasowang at redhat.com>

Thanks
>
> ---
> 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
>

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 at nvidia.com> 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 at nvidia.com>
>> Reviewed-by: Jiri Pirko <jiri at nvidia.com>
> 
> Acked-by: Jason Wang <jasowang at redhat.com>
> 
> 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
>>
>