On Mon, 21 Feb 2022 11:32:52 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote: > On Fri, Feb 18, 2022 at 5:00 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, 17 Feb 2022 15:19:44 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > On Thu, Feb 10, 2022 at 4:51 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > > > > > > > virtqueue_add() only supports virtual addresses, dma is completed in > > > > virtqueue_add(). > > > > > > > > In some scenarios (such as the AF_XDP scenario), DMA is completed in advance, so > > > > it is necessary for us to support passing the DMA address to virtqueue_add(). > > > > > > I'd suggest rename this feature as "unmanaged DMA". > > > > OK > > > > > > > > > > > > > Record this predma information in extra->flags, which can be skipped when > > > > executing dma unmap. > > > > > > Question still, can we use per-virtqueue flag instead of per > > > descriptor flag? If my memory is correct, the answer is yes in the > > > discussion for the previous version. > > > > > > > Yes. > > > > per-virtqueue? I guess it should be per-submit. > > > > This patch set only adds a flag to desc_extra[head].flags, so that we can know > > if we need to unmap dma when we detach. > > I meant if we can manage to make it per virtqueue, there's no need to > maintain per buffer flag. > Rethinking this question, I feel there is no essential difference between per virtqueue and per sgs. per virtqueue: 1. add buf: a. check vq->premapped for map every sg 2. detach: a. check vq->premaped for unmap per sgs: 1. add buf: a. check function parameter "premapped" for map every sg b. add flag to extra[head].flag 2. detach: a: check extra[head].flag for unmap Thanks. > So we know something that needs to be mapped by virtio core itself, > e.g the indirect page. Other than this, all the rest could be > pre-mapped. > > For vnet header, it could be mapped by virtio-net which could be still > treated as pre mapped DMA since it's not the virtio ring code. > > Anything I miss here? > > Thanks > > > > > > Thanks. > > > > > Thanks > > > > > > > > > > > v1: > > > > 1. All sgs requested at one time are required to be unified PREDMA, and several > > > > of them are not supported to be PREDMA > > > > 2. virtio_dma_map() is removed from this patch set and will be submitted > > > > together with the next time AF_XDP supports virtio dma > > > > 3. Added patch #2 #3 to remove the check for flags when performing unmap > > > > indirect desc > > > > > > > > Xuan Zhuo (6): > > > > virtio: rename vring_unmap_state_packed() to > > > > vring_unmap_extra_packed() > > > > virtio: remove flags check for unmap split indirect desc > > > > virtio: remove flags check for unmap packed indirect desc > > > > virtio: virtqueue_add() support predma > > > > virtio: split: virtqueue_add_split() support dma address > > > > virtio: packed: virtqueue_add_packed() support dma address > > > > > > > > drivers/virtio/virtio_ring.c | 199 ++++++++++++++++++++++------------- > > > > 1 file changed, 126 insertions(+), 73 deletions(-) > > > > > > > > -- > > > > 2.31.0 > > > > > > > > > > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
