[dpdk-dev] [PATCH 1/8] net/virtio: revert "virtio: fix restart"

Maxime Coquelin maxime.coquelin at redhat.com
Thu Nov 3 21:36:52 CET 2016

Hi Yuanhan,

On 11/03/2016 05:09 PM, Yuanhan Liu wrote:
> This reverts commit 9a0615af7746 ("virtio: fix restart"); conflict is
> manually addressed.
> Kyle reported an issue with above commit
>     qemu-kvm: Guest moved used index from 5 to 1
> with following steps,
>     1) Start my virtio interfaces
>     2) Send some traffic into/out of the interfaces
>     3) Stop the interfaces
>     4) Start the interfaces
>     5) Send some more traffic
> And here are some quotes from Kyle's analysis,
>     Prior to the patch, if an interface were stopped then started, without
>     restarting the application, the queues would be left as-is, because
>     hw->started would be set to 1. Now, calling stop sets hw->started to 0,
>     which means the next call to start will "touch the queues". This is the
>     unintended side-effect that causes the problem.

Maybe a good idea to explain what is the problem the revert aims to fix.
It does not seem to be clearly stated in the commit message.

> Fixes: 9a0615af7746 ("virtio: fix restart")
> Cc: Jianfeng Tan <jianfeng.tan at intel.com>
> Cc: <stable at dpdk.org>
> Reported-by: Kyle Larose <klarose at sandvine.com>
> Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>


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