On Fri, Jan 07, 2022 at 02:33:00PM +0800, Xuan Zhuo wrote: > virtqueue_add() only supports virtual addresses, dma is completed in > virtqueue_add(). > > In some scenarios (such as the AF_XDP scenario), DMA is completed in advance, so > it is necessary for us to support passing the DMA address to virtqueue_add(). > > This patch set 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; > > But the indirect desc does not have a corresponding extra, so the second and > third patches of this patch set are to allocate the corresponding extra while > allocating the indirect desc. Each desc must have a corresponding extra because > it is possible in an sgs some are advance DMA, while others are virtual > addresses. So we must allocate an extra for each indirect desc. I didn't realize AF_XDP didn't have space to stuff the header into. Jason, is that expected? It would be best to fix that, performance is best if header is linear with the data ... Or maybe we can reduce the use of indirect somewhat, at least while the ring is mostly empty? > Xuan Zhuo (6): > virtio: rename vring_unmap_state_packed() to > vring_unmap_extra_packed() > virtio: split: alloc indirect desc with extra > virtio: packed: alloc indirect desc with extra > virtio: split: virtqueue_add_split() support dma address > virtio: packed: virtqueue_add_packed() support dma address > virtio: add api virtio_dma_map() for advance dma > > drivers/virtio/virtio_ring.c | 387 ++++++++++++++++++++--------------- > include/linux/virtio.h | 9 + > 2 files changed, 232 insertions(+), 164 deletions(-) > > -- > 2.31.0 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
