On Tue, Mar 12, 2024 at 11:36 AM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > As discussed: > > http://lore.kernel.org/all/CACGkMEvq0No8QGC46U4mGsMtuD44fD_cfLcPaVmJ3rHYqRZxYg@xxxxxxxxxxxxxx > > If the virtio is premapped mode, the driver should manage the dma info by self. > So the virtio core should not store the dma info. We can release the memory used > to store the dma info. > > For virtio-net xmit queue, if the virtio-net maintains the dma info, > the virtio-net must allocate too much memory(19 * queue_size for per-queue), so > we do not plan to make the virtio-net to maintain the dma info by default. The > virtio-net xmit queue only maintain the dma info when premapped mode is enable > (such as AF_XDP is enable). > > So this patch set try to do: > > 1. make the virtio core to do not store the dma info I think you mean "make the virtio core to do not store the dma info when driver can do that" > - But if the desc_extra has not dma info, we face a new question, > it is hard to get the dma info of the desc with indirect flag. I guess you want to avoid allocating desc_extra array, otherwise you won't have this issue. How about keeping that? > For split mode, that is easy from desc, but for the packed mode, > it is hard to get the dma info from the desc. And hardening > the dma unmap is safe, we should store the dma info of indirect > descs when the virtio core does not store the bufer dma info. > > So I introduce the "structure the indirect desc table" to > allocate space to store dma info of the desc table. > > +struct vring_split_desc_indir { > + dma_addr_t addr; /* Descriptor Array DMA addr. */ > + u32 len; /* Descriptor Array length. */ > + u32 num; We can probably just reuse vring_desc_extra here with a known flag (read only for device). > + struct vring_desc desc[]; > +}; > > The follow patches to this: > * virtio_ring: packed: structure the indirect desc table > * virtio_ring: split: structure the indirect desc table > > - On the other side, in the umap handle, we mix the indirect descs with > other descs. That make things too complex. I found if we we distinguish > the descs with VRING_DESC_F_INDIRECT before unmap, thing will be clearer. > > The follow patches do this. > * virtio_ring: packed: remove double check of the unmap ops > * virtio_ring: split: structure the indirect desc table > > 2. make the virtio core to enable premapped mode by find_vqs() params > - Because the find_vqs() will try to allocate memory for the dma info. > If we set the premapped mode after find_vqs() and release the > dma info, that is odd. Thanks > > > Please review. > > Thanks > > v4: > 1. virtio-net xmit queue does not enable premapped mode by default > > v3: > 1. fix the conflict with the vp_modern_create_avq(). > > v2: > 1. change the dma item of virtio-net, every item have MAX_SKB_FRAGS + 2 addr + len pairs. > 2. introduce virtnet_sq_free_stats for __free_old_xmit > > v1: > 1. rename transport_vq_config to vq_transport_config > 2. virtio-net set dma meta number to (ring-size + 1)(MAX_SKB_FRGAS +2) > 3. introduce virtqueue_dma_map_sg_attrs > 4. separate vring_create_virtqueue to an independent commit > > Xuan Zhuo (10): > virtio_ring: introduce vring_need_unmap_buffer > virtio_ring: packed: remove double check of the unmap ops > virtio_ring: packed: structure the indirect desc table > virtio_ring: split: remove double check of the unmap ops > virtio_ring: split: structure the indirect desc table > virtio_ring: no store dma info when unmap is not needed > virtio: find_vqs: add new parameter premapped > virtio_ring: export premapped to driver by struct virtqueue > virtio_net: set premapped mode by find_vqs() > virtio_ring: virtqueue_set_dma_premapped support disable > > drivers/net/virtio_net.c | 57 +++-- > drivers/virtio/virtio_ring.c | 436 +++++++++++++++++++++------------- > include/linux/virtio.h | 3 +- > include/linux/virtio_config.h | 17 +- > 4 files changed, 307 insertions(+), 206 deletions(-) > > -- > 2.32.0.3.g01195cf9f >
