Re: [PATCH v1 0/6] virtio: support advance DMA

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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".

>
> 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.

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
>

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