On Mon, Mar 25, 2024 at 4:54 PM 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 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. > 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. > > 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 This doesn't apply cleany on vhost.git linux-next branch. Which tree is this based on? Thanks
