On Mon, 20 Feb 2023 13:38:24 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> 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?
The reason for not doing this, Virtio is not just using DMA_DEV to mapp, but
also check whether DMA is used.
>
> (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").
YES.
>
> > + 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.
Because I did not use this interface, I did not export it.
Thanks.
>
> 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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