On Fri, Jun 02, 2023 at 05:21:56PM +0800, Xuan Zhuo wrote: > ## About DMA APIs > > Now, virtio may can not work with DMA APIs when virtio features do not have > VIRTIO_F_ACCESS_PLATFORM. > > 1. I tried to let DMA APIs return phy address by virtio-device. But DMA APIs just > work with the "real" devices. > 2. I tried to let xsk support callballs to get phy address from virtio-net > driver as the dma address. But the maintainers of xsk may want to use dma-buf > to replace the DMA APIs. I think that may be a larger effort. We will wait > too long. > > So rethinking this, firstly, we can support premapped-dma only for devices with > VIRTIO_F_ACCESS_PLATFORM. In the case of af-xdp, if the users want to use it, > they have to update the device to support VIRTIO_F_RING_RESET, and they can also > enable the device's VIRTIO_F_ACCESS_PLATFORM feature. > > Thanks for the help from Christoph. > > ================= > > XDP socket(AF_XDP) is an excellent bypass kernel network framework. The zero > copy feature of xsk (XDP socket) needs to be supported by the driver. The > performance of zero copy is very good. > > ENV: Qemu with vhost. > > vhost cpu | Guest APP CPU |Guest Softirq CPU | PPS > -----------------------------|---------------|------------------|------------ > xmit by sockperf: 90% | 100% | | 318967 > xmit by xsk: 100% | 30% | 33% | 1192064 > recv by sockperf: 100% | 68% | 100% | 692288 > recv by xsk: 100% | 33% | 43% | 771670 > > Before achieving the function of Virtio-Net, we also have to let virtio core > support these features: So by itself, this doesn't do this. But what effect does all this overhead have on performance? > 1. virtio core support premapped > 2. virtio core support reset per-queue > 3. introduce DMA APIs to virtio core > > Please review. > > Thanks. > > v10: > 1. support to set vq to premapped mode, then the vq just handles the premapped request. > 2. virtio-net support to do dma mapping in advance > > v9: > 1. use flag to distinguish the premapped operations. no do judgment by sg. > > v8: > 1. vring_sg_address: check by sg_page(sg) not dma_address. Because 0 is a valid dma address > 2. remove unused code from vring_map_one_sg() > > v7: > 1. virtqueue_dma_dev() return NULL when virtio is without DMA API. > > v6: > 1. change the size of the flags to u32. > > v5: > 1. fix for error handler > 2. add flags to record internal dma mapping > > v4: > 1. rename map_inter to dma_map_internal > 2. fix: Excess function parameter 'vq' description in 'virtqueue_dma_dev' > > v3: > 1. add map_inter to struct desc state to reocrd whether virtio core do dma map > > v2: > 1. based on sgs[0]->dma_address to judgment is premapped > 2. based on extra.addr to judgment to do unmap for no-indirect desc > 3. based on indir_desc to judgment to do unmap for indirect desc > 4. rename virtqueue_get_dma_dev to virtqueue_dma_dev > > v1: > 1. expose dma device. NO introduce the api for dma and sync > 2. split some commit for review. > > > > > Xuan Zhuo (10): > virtio_ring: put mapping error check in vring_map_one_sg > virtio_ring: introduce virtqueue_set_premapped() > virtio_ring: split: support add premapped buf > virtio_ring: packed: support add premapped buf > virtio_ring: split-detach: support return dma info to driver > virtio_ring: packed-detach: support return dma info to driver > virtio_ring: introduce helpers for premapped > virtio_ring: introduce virtqueue_dma_dev() > virtio_ring: introduce virtqueue_add_sg() > virtio_net: support dma premapped > > drivers/net/virtio_net.c | 163 ++++++++++-- > drivers/virtio/virtio_ring.c | 493 +++++++++++++++++++++++++++++++---- > include/linux/virtio.h | 34 +++ > 3 files changed, 612 insertions(+), 78 deletions(-) > > -- > 2.32.0.3.g01195cf9f
