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

[Maxime Coquelin]

On 9/10/20 8:11 PM, Ilya Maximets wrote:
> 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."

Yes, Ilya is right.

With above fixed, the patch looks good to me:
Acked-by: Maxime Coquelin <maxime.coquelin at redhat.com>

Thanks,
Maxime

> Best regards, Ilya Maximets.
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