On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> Added virtio_dma_map() to map DMA addresses for virtual memory in
> advance. The purpose is to keep memory mapped across multiple add/get
> buf operations.
I wonder if instead of exporting helpers like this, it might be simple
to just export dma_dev then the upper layer can use DMA API at will?
(Otherwise the DMA helpers need to grow/shrink as the DMA API evolves?)
>
> Added virtio_dma_unmap() for unmap DMA address.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 92 ++++++++++++++++++++++++++++++++++++
> include/linux/virtio.h | 9 ++++
> 2 files changed, 101 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index cd9364eb2345..855338609c7f 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -3172,4 +3172,96 @@ const struct vring *virtqueue_get_vring(struct virtqueue *vq)
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_vring);
>
> +/**
> + * virtio_dma_map_page - get the DMA addr of the memory for virtio device
> + * @dev: virtio device
> + * @page: the page of the memory to DMA
> + * @offset: the offset of the memory inside page
> + * @length: memory length
> + * @dir: DMA direction
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers virtio
> + * core handles DMA API internally.
> + *
> + * Returns the DMA addr. DMA_MAPPING_ERROR means error.
> + */
> +dma_addr_t virtio_dma_map_page(struct device *dev, struct page *page, size_t offset,
> + unsigned int length, enum dma_data_direction dir)
> +{
This (and the reset) needs to be done per virtqueue instead per device
after b0e504e5505d184b0be248b7dcdbe50b79f03758 ("virtio_ring: per
virtqueue dma device").
> + struct virtio_device *vdev = dev_to_virtio(dev);
> +
> + if (!vring_use_dma_api(vdev))
> + return page_to_phys(page) + offset;
> +
> + return dma_map_page(vdev->dev.parent, page, offset, length, dir);
> +}
Need either inline or EXPORT_SYMBOL_GPL() here.
Thanks
> +
> +/**
> + * virtio_dma_map - get the DMA addr of the memory for virtio device
> + * @dev: virtio device
> + * @addr: the addr to DMA
> + * @length: memory length
> + * @dir: DMA direction
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers virtio
> + * core handles DMA API internally.
> + *
> + * Returns the DMA addr.
> + */
> +dma_addr_t virtio_dma_map(struct device *dev, void *addr, unsigned int length,
> + enum dma_data_direction dir)
> +{
> + struct page *page;
> + size_t offset;
> +
> + page = virt_to_page(addr);
> + offset = offset_in_page(addr);
> +
> + return virtio_dma_map_page(dev, page, offset, length, dir);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_map);
> +
> +/**
> + * virtio_dma_mapping_error - check dma address
> + * @dev: virtio device
> + * @addr: DMA address
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers virtio
> + * core handles DMA API internally.
> + *
> + * Returns 0 means dma valid. Other means invalid dma address.
> + */
> +int virtio_dma_mapping_error(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_mapping_error(vdev->dev.parent, addr);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_mapping_error);
> +
> +/**
> + * virtio_dma_unmap - unmap DMA addr
> + * @dev: virtio device
> + * @dma: DMA address
> + * @length: memory length
> + * @dir: DMA direction
> + *
> + * This API is only for pre-mapped buffers, for non premapped buffers virtio
> + * core handles DMA API internally.
> + */
> +void virtio_dma_unmap(struct device *dev, dma_addr_t dma, unsigned int length,
> + enum dma_data_direction dir)
> +{
> + struct virtio_device *vdev = dev_to_virtio(dev);
> +
> + if (!vring_use_dma_api(vdev))
> + return;
> +
> + dma_unmap_page(vdev->dev.parent, dma, length, dir);
> +}
> +EXPORT_SYMBOL_GPL(virtio_dma_unmap);
> +
> MODULE_LICENSE("GPL");
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 3ebb346ebb7c..b5fa71476737 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -9,6 +9,7 @@
> #include <linux/device.h>
> #include <linux/mod_devicetable.h>
> #include <linux/gfp.h>
> +#include <linux/dma-mapping.h>
>
> /**
> * struct virtqueue - a queue to register buffers for sending or receiving.
> @@ -216,4 +217,12 @@ void unregister_virtio_driver(struct virtio_driver *drv);
> #define module_virtio_driver(__virtio_driver) \
> module_driver(__virtio_driver, register_virtio_driver, \
> unregister_virtio_driver)
> +
> +dma_addr_t virtio_dma_map_page(struct device *dev, struct page *page, size_t offset,
> + unsigned int length, enum dma_data_direction dir);
> +dma_addr_t virtio_dma_map(struct device *dev, void *addr, unsigned int length,
> + enum dma_data_direction dir);
> +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);
> #endif /* _LINUX_VIRTIO_H */
> --
> 2.32.0.3.g01195cf9f
>
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