[dpdk-dev] [PATCH v3 1/8] eal: introduce DMA memory barriers

Andrew Rybchenko arybchenko at solarflare.com
Fri Jan 19 08:16:17 CET 2018


On 01/19/2018 03:44 AM, Yongseok Koh wrote:
> This commit introduces rte_dma_wmb() and rte_dma_rmb(), in order to
> guarantee the ordering of coherent shared memory between the CPU and a DMA
> capable device.
>
> Signed-off-by: Yongseok Koh <yskoh at mellanox.com>

Acked-by: Andrew Rybchenko <arybchenko at solarflare.com>

It is already really good. Many thanks.

Maybe it would be useful to:
  - avoid duplication of so long explanations (put in in one place and 
add reference?)
  - explain why it is bound to DMA or call it in a different way, since 
right now it is bound
    to coherent-mapped IO (rte_cio_rmb() ?). Yes, I see benefits to 
follow Linux
    terminology, but may be DPDK can do better :) I just add my 
concerns, but let
    EAL code maintainers to decide
  - as I understand right now there is no control over DMA mapping since
    mapping is done by UIO/VFIO drivers. Should documentation be updated 
that
    DMA mapping is assumed to be coherent?
  - when it is applied, may be it makes sense to send HEADS UP to dev@,
    it definitely deserves to be mentioned in the release notes

<...>


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