Re: [dpdk-dev] [PATCH v3 0/7] virtio_user as an alternative exception path

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 1/9/2017 10:06 PM, Bruce Richardson wrote:
> On Wed, Jan 04, 2017 at 03:59:19AM +0000, Jianfeng Tan wrote:
>> v3:
>>    - Drop the patch to postpone driver ok sending patch, superseded it
>>      with a bug fix to disable all virtqueues and re-init the device.
>>      (you might wonder why not just send reset owner msg. Under my test,
>>       it causes spinlock deadlock problem when killing the program).
>>    - Avoid compiling error on 32-bit system for pointer convert.
>>    - Fix a bug in patch "abstract virtio user backend ops", vhostfd is
>>      not properly assigned.
>>    - Fix a "MQ cannot be used" bug in v2, which is related to strip
>>      some feature bits that vhost kernel does not recognize.
>>    - Update release note.
>>
>> v2: (Lots of them are from yuanhan's comment)
>>    - Add offloding feature.
>>    - Add multiqueue support.
>>    - Add a new patch to postpone the sending of driver ok notification.
>>    - Put fix patch ahead of the whole patch series.
>>    - Split original 0001 patch into 0003 and 0004 patches.
>>    - Remove the original vhost_internal design, just add those into
>>      struct virtio_user_dev for simplicity.
>>    - Reword "control" to "send_request".
>>    - Reword "host_features" to "device_features".
>>
>> In v16.07, we upstreamed a virtual device, virtio_user (with vhost-user
>> as the backend). The path to go with a vhost-kernel backend has been
>> dropped for bad performance comparing to vhost-user and code simplicity.
>>
>> But after a second thought, virtio_user + vhost-kernel is a good
>> candidate as an exceptional path, such as KNI, which exchanges packets
>> with kernel networking stack.
>>    - maintenance: vhost-net (kernel) is upstreamed and extensively used
>>      kernel module. We don't need any out-of-tree module like KNI.
>>    - performance: as with KNI, this solution would use one or more
>>      kthreads to send/receive packets from user space DPDK applications,
>>      which has little impact on user space polling thread (except that
>>      it might enter into kernel space to wake up those kthreads if
>>      necessary).
>>    - features: vhost-net is born to be a networking solution, which has
>>      lots of networking related featuers, like multi queue, tso, multi-seg
>>      mbuf, etc.
>>
>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>>
> Sounds great. However, I think we'll need a how-to doc for this to help
> people get it up and running as a KNI replacement for packets to/from
> the kernel. Any plans to draw up such a doc? It would be good to include
> it in this patchset.

I was planning to do that in separate patchset. But I agree with you 
that it's better to do that in this patchset.

Thanks,
Jianfeng

>
> /Bruce