Re: [PATCH v0 1/1] doc: announce inter-device DMA capability support in dmadev

[fengchengwen <fengchengwen@huawei.com>]

Hi Vamsi,

From the commit log, I guess this commit mainly want to meet following case:

     ---------------             ----------------
     |  Container  |             |  VirtMachine |
     |             |             |              |
     |  dmadev-1   |             |   dmadev2    |
     ---------------             ----------------
           |                            |
           ------------------------------

App run in the container could launch DMA transfer from local buffer to the VirtMachine by config
dmadev-1/2 (the dmadev-1/2 are passthrough to diffent OS domain).

Could you explain how to use it from application perspective (for example address translation) and
application & hardware restrictions?


BTW: In this case, there are two OS domain communication, and I remember there are also inter-process
DMA RFC, so maybe we could design more generic solution if you provide more info.

Thanks

On 2025/7/10 16:51, Vamsi Krishna wrote:
> From: Vamsi Attunuru <vattunuru@marvell.com>
> 
> Modern DMA hardware supports data transfer between multiple
> DMA devices, enabling data communication across isolated domains or
> containers. To facilitate this, the ``dmadev`` library requires changes
> to allow devices to register with or unregisters from DMA groups for
> inter-device communication. This feature is planned for inclusion
> in DPDK 25.11.
> 
> Signed-off-by: Vamsi Attunuru <vattunuru@marvell.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index e2d4125308..46836244dd 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -152,3 +152,10 @@ Deprecation Notices
>  * bus/vmbus: Starting DPDK 25.11, all the vmbus API defined in
>    ``drivers/bus/vmbus/rte_bus_vmbus.h`` will become internal to DPDK.
>    Those API functions are used internally by DPDK core and netvsc PMD.
> +
> +* dmadev: a new capability flag ``RTE_DMA_CAPA_INTER_DEV`` will be added
> +  to advertise DMA device's inter-device DMA copy capability. To enable
> +  this functionality, a few dmadev APIs will be added to configure the DMA
> +  access groups, facilitating coordinated data communication between devices.
> +  A new ``dev_idx`` field will be added to the ``struct rte_dma_vchan_conf``
> +  structure to configure a vchan for data transfers between any two DMA devices.