On Fri, Jul 28, 2023 at 02:02:33PM +0800, Xuan Zhuo wrote: > On Tue, 25 Jul 2023 19:07:23 +0800, Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > On Tue, 25 Jul 2023 03:34:34 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > On Tue, Jul 25, 2023 at 10:13:48AM +0800, Xuan Zhuo wrote: > > > > On Mon, 24 Jul 2023 09:43:42 -0700, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > > On Thu, Jul 20, 2023 at 01:21:07PM -0400, Michael S. Tsirkin wrote: > > > > > > Well I think we can add wrappers like virtio_dma_sync and so on. > > > > > > There are NOP for non-dma so passing the dma device is harmless. > > > > > > > > > > Yes, please. > > > > > > > > > > > > I am not sure I got this fully. > > > > > > > > Are you mean this: > > > > https://lore.kernel.org/all/20230214072704.126660-8-xuanzhuo@xxxxxxxxxxxxxxxxx/ > > > > https://lore.kernel.org/all/20230214072704.126660-9-xuanzhuo@xxxxxxxxxxxxxxxxx/ > > > > > > > > Then the driver must do dma operation(map and sync) by these virtio_dma_* APIs. > > > > No care the device is non-dma device or dma device. > > > > > > yes > > > > > > > Then the AF_XDP must use these virtio_dma_* APIs for virtio device. > > > > > > We'll worry about AF_XDP when the patch is posted. > > > > YES. > > > > We discussed it. They voted 'no'. > > > > http://lore.kernel.org/all/20230424082856.15c1e593@xxxxxxxxxx > > > Hi guys, this topic is stuck again. How should I proceed with this work? > > Let me briefly summarize: > 1. The problem with adding virtio_dma_{map, sync} api is that, for AF_XDP and > the driver layer, we need to support these APIs. The current conclusion of > AF_XDP is no. > > 2. Set dma_set_mask_and_coherent, then we can use DMA API uniformly inside > driver. This idea seems to be inconsistent with the framework design of DMA. The > conclusion is no. > > 3. We noticed that if the virtio device supports VIRTIO_F_ACCESS_PLATFORM, it > uses DMA API. And this type of device is the future direction, so we only > support DMA premapped for this type of virtio device. The problem with this > solution is that virtqueue_dma_dev() only returns dev in some cases, because > VIRTIO_F_ACCESS_PLATFORM is supported in such cases. Otherwise NULL is returned. > This option is currently NO. > > So I'm wondering what should I do, from a DMA point of view, is there any > solution in case of using DMA API? > > Thank you I think it's ok at this point, Christoph just asked you to add wrappers for map/unmap for use in virtio code. Seems like a cosmetic change, shouldn't be hard. Otherwise I haven't seen significant comments. Christoph do I summarize what you are saying correctly? -- MST
