On Mon, 21 Feb 2022 11:32:52 +0800, Jason Wang <[email protected]> wrote: > On Fri, Feb 18, 2022 at 5:00 PM Xuan Zhuo <[email protected]> wrote: > > > > On Thu, 17 Feb 2022 15:19:44 +0800, Jason Wang <[email protected]> wrote: > > > On Thu, Feb 10, 2022 at 4:51 PM Xuan Zhuo <[email protected]> > > > 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. > > 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?
I guess, your understanding is that after the queue is reset, the queue is used by xsk(AF_XDP), then all commits to this vq are premapped amd address. This is ok for rx. But for tx, just like XDP TX, although vq is used by xsk, the kernel also passes skb to it at the same time. It is shared. We can guarantee that the sg of the sgs submitted at one time uses the premapped dma address or virtual address uniformly. It is not guaranteed that all the sgs to the vq are uniform Thanks. > > 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 [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
