On Tue, 21 Feb 2023 09:51:07 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Mon, Feb 20, 2023 at 3:02 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > 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.
>
> We should let the DMA API decide by exporting a correct dma_dev. E.g
> when ACCESS_PLATFORM is not negotiated, advertising a DMA dev without
> dma_ops.
In XSK, we need to pass a device to XSK.
If vdev->dev is passed, we can't get dma_dev in XSK. Because each VQ has a
dma_dev. So we should pass dma_dev to XSK. But how do we determine whether to
use DMA_OPS based on dma_dev?
At present, my API design, the caller should determine whether it is a Virtio
device. If we also need the caller to determine whether to use DMA_OPS, this is
too unfriendly for the caller.
Thanks.
>
> Thanks
>
> >
> >
> > >
> > > (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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