[ovs-dev] [PATCH v2 1/1] DPDK: Remove support for vhost-user zero-copy.

Ilya Maximets i.maximets at ovn.org
Thu Sep 10 18:11:52 UTC 2020


On 9/10/20 7:30 PM, Ian Stokes wrote:
> Support for vhost-user dequeue zero-copy was deprecated in OVS 2.14 with
> the aim of removing it for OVS 2.15.
> 
> OVS only supports zero copy for vhost client mode, as such it will cease
> to function due to DPDK commit [1]
> 
> Also DPDK is set to remove zero-copy functionality in DPDK 20.11 as
> referenced by commit [2]
> 
> As such remove support from OVS.
> 
> [1] 715070ea10e6 ("vhost: prevent zero-copy with incompatible client mode")
> [2] d21003c9dafa ("doc: announce removal of vhost zero-copy dequeue")
> 
> Signed-off-by: Ian Stokes <ian.stokes at intel.com>
> 
> ---
> v1 -> v2
> * Remove reference to zero copy in vhost post copy documentation.
> * Add DPDK commits that have influenced OVS decision to remove support
>   for zero-copy.
> * Correct NEWS to reference removal rather than deprecation of zc.
> ---
>  Documentation/topics/dpdk/vhost-user.rst | 76 --------------------------------
>  NEWS                                     |  2 +
>  lib/netdev-dpdk.c                        | 25 -----------
>  vswitchd/vswitch.xml                     | 11 -----
>  4 files changed, 2 insertions(+), 112 deletions(-)
> 
> diff --git a/Documentation/topics/dpdk/vhost-user.rst b/Documentation/topics/dpdk/vhost-user.rst
> index 4af738d11..3be8f8b5e 100644
> --- a/Documentation/topics/dpdk/vhost-user.rst
> +++ b/Documentation/topics/dpdk/vhost-user.rst
> @@ -339,10 +339,6 @@ The default value is ``false``.
>      migration recovery was fixed for post-copy in 3.0 and few additional bug
>      fixes (like userfaulfd leak) was released in 3.0.1.
>  
> -    DPDK Post-copy feature requires avoiding to populate the guest memory
> -    (application must not call mlock* syscall). So enabling mlockall and
> -    dequeue zero-copy features is mis-compatible with post-copy feature.

The part about mlockall is still valid, only zero-copy related words should be
removed, e.g. "So enabling mlockall is mis-compatible with post-copy feature."

Best regards, Ilya Maximets.


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