On Mon, 10 Jan 2022 14:45:42 +0800, Jason Wang <[email protected]> wrote: > > 在 2022/1/7 下午2:33, Xuan Zhuo 写道: > > virtqueue_add_split() only supports virtual addresses, dma is completed > > in virtqueue_add_split(). > > > > In some scenarios (such as the AF_XDP scenario), the memory is allocated > > and DMA is completed in advance, so it is necessary for us to support > > passing the DMA address to virtqueue_add_split(). > > > > This patch stipulates that if sg->dma_address is not NULL, use this > > address as the DMA address. And record this information in extra->flags, > > which can be skipped when executing dma unmap. > > > > extra->flags |= VRING_DESC_F_PREDMA; > > > I think we need another name other than the VRING_DESC_F prefix since > it's for the flag defined in the spec. May VIRTIO_DESC_F_PREDMA. >
OK. > Thanks > > > > > > This relies on the previous patch, in the indirect scenario, for each > > desc allocated, an extra is allocated at the same time. > > > > Signed-off-by: Xuan Zhuo <[email protected]> > > --- > > drivers/virtio/virtio_ring.c | 28 ++++++++++++++++++++++++---- > > 1 file changed, 24 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 7420741cb750..add8430d9678 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -66,6 +66,9 @@ > > #define LAST_ADD_TIME_INVALID(vq) > > #endif > > > > +/* This means the buffer dma is pre-alloc. Just used by vring_desc_extra */ > > +#define VRING_DESC_F_PREDMA (1 << 15) > > + > > struct vring_desc_extra { > > dma_addr_t addr; /* Descriptor DMA addr. */ > > u32 len; /* Descriptor length. */ > > @@ -336,11 +339,19 @@ static inline struct device *vring_dma_dev(const > > struct vring_virtqueue *vq) > > return vq->vq.vdev->dev.parent; > > } > > > > +static inline bool sg_is_predma(struct scatterlist *sg) > > +{ > > + return !!sg->dma_address; > > +} > > + > > /* Map one sg entry. */ > > static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq, > > struct scatterlist *sg, > > enum dma_data_direction direction) > > { > > + if (sg_is_predma(sg)) > > + return sg_dma_address(sg); > > + > > if (!vq->use_dma_api) > > return (dma_addr_t)sg_phys(sg); > > > > @@ -396,6 +407,9 @@ static unsigned int vring_unmap_one_split(const struct > > vring_virtqueue *vq, > > (flags & VRING_DESC_F_WRITE) ? > > DMA_FROM_DEVICE : DMA_TO_DEVICE); > > } else { > > + if (flags & VRING_DESC_F_PREDMA) > > + goto out; > > + > > dma_unmap_page(vring_dma_dev(vq), > > extra->addr, > > extra->len, > > @@ -441,7 +455,8 @@ static inline unsigned int > > virtqueue_add_desc_split(struct virtqueue *vq, > > unsigned int i, > > dma_addr_t addr, > > unsigned int len, > > - u16 flags) > > + u16 flags, > > + bool predma) > > { > > struct vring_virtqueue *vring = to_vvq(vq); > > struct vring_desc_extra *extra; > > @@ -468,6 +483,9 @@ static inline unsigned int > > virtqueue_add_desc_split(struct virtqueue *vq, > > extra->len = len; > > extra->flags = flags; > > > > + if (predma) > > + extra->flags |= VRING_DESC_F_PREDMA; > > + > > return next; > > } > > > > @@ -547,7 +565,8 @@ static inline int virtqueue_add_split(struct virtqueue > > *_vq, > > * table since it use stream DMA mapping. > > */ > > i = virtqueue_add_desc_split(_vq, in, i, addr, > > sg->length, > > - VRING_DESC_F_NEXT); > > + VRING_DESC_F_NEXT, > > + sg_is_predma(sg)); > > } > > } > > for (; n < (out_sgs + in_sgs); n++) { > > @@ -563,7 +582,8 @@ static inline int virtqueue_add_split(struct virtqueue > > *_vq, > > i = virtqueue_add_desc_split(_vq, in, i, addr, > > sg->length, > > VRING_DESC_F_NEXT | > > - VRING_DESC_F_WRITE); > > + VRING_DESC_F_WRITE, > > + sg_is_predma(sg)); > > } > > } > > /* Last one doesn't continue. */ > > @@ -582,7 +602,7 @@ static inline int virtqueue_add_split(struct virtqueue > > *_vq, > > > > virtqueue_add_desc_split(_vq, NULL, head, addr, > > total_sg * sizeof(struct vring_desc), > > - VRING_DESC_F_INDIRECT); > > + VRING_DESC_F_INDIRECT, false); > > } > > > > /* We're using some buffers from the free list. */ > _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
