On Tue, Mar 12, 2024 at 11:35:47AM +0800, Xuan Zhuo wrote:
> As discussed:
>
> http://lore.kernel.org/all/cacgkmevq0no8qgc46u4mgsmtud44fd_cflcpavmj3rhyqrz...@mail.gmail.com
>
> 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).
This landed when merge window was open already so I'm deferring this
to the next merge window, just to be safe. Jason can you review please?
> So this patch set try to do:
>
> 1. make the virtio core to do not store the dma info
> - 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.
> 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;
> + 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.
>
>
> 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
