Virtualization - Feb 2023 - [PATCH vhost 08/10] virtio_ring: introduce dma sync api for virtio

On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo <xuanzhuo at linux.alibaba.com>
wrote:
>
> These API has been introduced:
>
> * virtio_dma_need_sync
> * virtio_dma_sync_single_range_for_cpu
> * virtio_dma_sync_single_range_for_device
What's the advantages of exporting internal logic like
virtio_dma_need_sync() over hiding it in
virtio_dma_sync_single_range_for_cpu() and
virtio_dma_sync_single_range_for_device()?

Thanks

>
> These APIs can be used together with the premapped mechanism to sync the
> DMA address.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> ---
>  drivers/virtio/virtio_ring.c | 70 ++++++++++++++++++++++++++++++++++++
>  include/linux/virtio.h       |  8 +++++
>  2 files changed, 78 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 855338609c7f..84129b8c3e2a 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -3264,4 +3264,74 @@ void virtio_dma_unmap(struct device *dev, dma_addr_t
dma, unsigned int length,
>  }
>  EXPORT_SYMBOL_GPL(virtio_dma_unmap);
>
> +/**
> + * virtio_dma_need_sync - check a dma address needs sync
> + * @dev: virtio device
> + * @addr: DMA address
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> + * core handles DMA API internally.
> + */
> +bool virtio_dma_need_sync(struct device *dev, dma_addr_t addr)
> +{
> +       struct virtio_device *vdev = dev_to_virtio(dev);
> +
> +       if (!vring_use_dma_api(vdev))
> +               return 0;
> +
> +       return dma_need_sync(vdev->dev.parent, addr);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_need_sync);
> +
> +/**
> + * virtio_dma_sync_single_range_for_cpu - dma sync for cpu
> + * @dev: virtio device
> + * @addr: DMA address
> + * @offset: DMA address offset
> + * @size: mem size for sync
> + * @dir: DMA direction
> + *
> + * Before calling this function, use virtio_dma_need_sync() to confirm
that the
> + * DMA address really needs to be synchronized
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> + * core handles DMA API internally.
> + */
> +void virtio_dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t
addr,
> +                                         unsigned long offset, size_t
size,
> +                                         enum dma_data_direction dir)
> +{
> +       struct virtio_device *vdev = dev_to_virtio(dev);
> +
> +       dma_sync_single_range_for_cpu(vdev->dev.parent, addr, offset,
> +                                     size, DMA_BIDIRECTIONAL);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_sync_single_range_for_cpu);
> +
> +/**
> + * virtio_dma_sync_single_range_for_device - dma sync for device
> + * @dev: virtio device
> + * @addr: DMA address
> + * @offset: DMA address offset
> + * @size: mem size for sync
> + * @dir: DMA direction
> + *
> + * Before calling this function, use virtio_dma_need_sync() to confirm
that the
> + * DMA address really needs to be synchronized
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> + * core handles DMA API internally.
> + */
> +void virtio_dma_sync_single_range_for_device(struct device *dev,
> +                                            dma_addr_t addr,
> +                                            unsigned long offset, size_t
size,
> +                                            enum dma_data_direction dir)
> +{
> +       struct virtio_device *vdev = dev_to_virtio(dev);
> +
> +       dma_sync_single_range_for_device(vdev->dev.parent, addr, offset,
> +                                        size, DMA_BIDIRECTIONAL);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_sync_single_range_for_device);
> +
>  MODULE_LICENSE("GPL");
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index b5fa71476737..d0e707d744a0 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -225,4 +225,12 @@ dma_addr_t virtio_dma_map(struct device *dev, void
*addr, unsigned int length,
>  int virtio_dma_mapping_error(struct device *dev, dma_addr_t addr);
>  void virtio_dma_unmap(struct device *dev, dma_addr_t dma, unsigned int
length,
>                       enum dma_data_direction dir);
> +bool virtio_dma_need_sync(struct device *dev, dma_addr_t addr);
> +void virtio_dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t
addr,
> +                                         unsigned long offset, size_t
size,
> +                                         enum dma_data_direction dir);
> +void virtio_dma_sync_single_range_for_device(struct device *dev,
> +                                            dma_addr_t addr,
> +                                            unsigned long offset, size_t
size,
> +                                            enum dma_data_direction dir);
>  #endif /* _LINUX_VIRTIO_H */
> --
> 2.32.0.3.g01195cf9f
>

On Mon, 20 Feb 2023 13:38:20 +0800, Jason Wang <jasowang at redhat.com>
wrote:
> On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo <xuanzhuo at
linux.alibaba.com> wrote:
> >
> > These API has been introduced:
> >
> > * virtio_dma_need_sync
> > * virtio_dma_sync_single_range_for_cpu
> > * virtio_dma_sync_single_range_for_device
>
> What's the advantages of exporting internal logic like
> virtio_dma_need_sync() over hiding it in
> virtio_dma_sync_single_range_for_cpu() and
> virtio_dma_sync_single_range_for_device()?
Sorry, I didn't understand it.

Thanks.
>
> Thanks
>
>
> >
> > These APIs can be used together with the premapped mechanism to sync
the
> > DMA address.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> > ---
> >  drivers/virtio/virtio_ring.c | 70
++++++++++++++++++++++++++++++++++++
> >  include/linux/virtio.h       |  8 +++++
> >  2 files changed, 78 insertions(+)
> >
> > diff --git a/drivers/virtio/virtio_ring.c
b/drivers/virtio/virtio_ring.c
> > index 855338609c7f..84129b8c3e2a 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -3264,4 +3264,74 @@ void virtio_dma_unmap(struct device *dev,
dma_addr_t dma, unsigned int length,
> >  }
> >  EXPORT_SYMBOL_GPL(virtio_dma_unmap);
> >
> > +/**
> > + * virtio_dma_need_sync - check a dma address needs sync
> > + * @dev: virtio device
> > + * @addr: DMA address
> > + *
> > + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> > + * core handles DMA API internally.
> > + */
> > +bool virtio_dma_need_sync(struct device *dev, dma_addr_t addr)
> > +{
> > +       struct virtio_device *vdev = dev_to_virtio(dev);
> > +
> > +       if (!vring_use_dma_api(vdev))
> > +               return 0;
> > +
> > +       return dma_need_sync(vdev->dev.parent, addr);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_dma_need_sync);
> > +
> > +/**
> > + * virtio_dma_sync_single_range_for_cpu - dma sync for cpu
> > + * @dev: virtio device
> > + * @addr: DMA address
> > + * @offset: DMA address offset
> > + * @size: mem size for sync
> > + * @dir: DMA direction
> > + *
> > + * Before calling this function, use virtio_dma_need_sync() to
confirm that the
> > + * DMA address really needs to be synchronized
> > + *
> > + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> > + * core handles DMA API internally.
> > + */
> > +void virtio_dma_sync_single_range_for_cpu(struct device *dev,
dma_addr_t addr,
> > +                                         unsigned long offset, size_t
size,
> > +                                         enum dma_data_direction dir)
> > +{
> > +       struct virtio_device *vdev = dev_to_virtio(dev);
> > +
> > +       dma_sync_single_range_for_cpu(vdev->dev.parent, addr,
offset,
> > +                                     size, DMA_BIDIRECTIONAL);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_dma_sync_single_range_for_cpu);
> > +
> > +/**
> > + * virtio_dma_sync_single_range_for_device - dma sync for device
> > + * @dev: virtio device
> > + * @addr: DMA address
> > + * @offset: DMA address offset
> > + * @size: mem size for sync
> > + * @dir: DMA direction
> > + *
> > + * Before calling this function, use virtio_dma_need_sync() to
confirm that the
> > + * DMA address really needs to be synchronized
> > + *
> > + * This API is only for pre-mapped buffers, for non premapped buffers
virtio
> > + * core handles DMA API internally.
> > + */
> > +void virtio_dma_sync_single_range_for_device(struct device *dev,
> > +                                            dma_addr_t addr,
> > +                                            unsigned long offset,
size_t size,
> > +                                            enum dma_data_direction
dir)
> > +{
> > +       struct virtio_device *vdev = dev_to_virtio(dev);
> > +
> > +       dma_sync_single_range_for_device(vdev->dev.parent, addr,
offset,
> > +                                        size, DMA_BIDIRECTIONAL);
> > +}
> > +EXPORT_SYMBOL_GPL(virtio_dma_sync_single_range_for_device);
> > +
> >  MODULE_LICENSE("GPL");
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index b5fa71476737..d0e707d744a0 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -225,4 +225,12 @@ dma_addr_t virtio_dma_map(struct device *dev,
void *addr, unsigned int length,
> >  int virtio_dma_mapping_error(struct device *dev, dma_addr_t addr);
> >  void virtio_dma_unmap(struct device *dev, dma_addr_t dma, unsigned
int length,
> >                       enum dma_data_direction dir);
> > +bool virtio_dma_need_sync(struct device *dev, dma_addr_t addr);
> > +void virtio_dma_sync_single_range_for_cpu(struct device *dev,
dma_addr_t addr,
> > +                                         unsigned long offset, size_t
size,
> > +                                         enum dma_data_direction
dir);
> > +void virtio_dma_sync_single_range_for_device(struct device *dev,
> > +                                            dma_addr_t addr,
> > +                                            unsigned long offset,
size_t size,
> > +                                            enum dma_data_direction
dir);
> >  #endif /* _LINUX_VIRTIO_H */
> > --
> > 2.32.0.3.g01195cf9f
> >
>