netdev - Re: [PATCH net 5/6] virtio-net: fix the vq coalescing setting for vq resize

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Message-ID: <c95274cd-d119-402b-baf1-0c500472c9fb@linux.alibaba.com>
Date: Fri, 22 Sep 2023 13:02:42 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
 "Michael S . Tsirkin" <mst@...hat.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Gavin Li <gavinl@...dia.com>
Subject: Re: [PATCH net 5/6] virtio-net: fix the vq coalescing setting for vq
 resize

在 2023/9/22 下午12:29, Jason Wang 写道:
> On Tue, Sep 19, 2023 at 3:49 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>> According to the definition of virtqueue coalescing spec[1]:
>>
>>    Upon disabling and re-enabling a transmit virtqueue, the device MUST set
>>    the coalescing parameters of the virtqueue to those configured through the
>>    VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver did not set
>>    any TX coalescing parameters, to 0.
>>
>>    Upon disabling and re-enabling a receive virtqueue, the device MUST set
>>    the coalescing parameters of the virtqueue to those configured through the
>>    VIRTIO_NET_CTRL_NOTF_COAL_RX_SET command, or, if the driver did not set
>>    any RX coalescing parameters, to 0.
>>
>> We need to add this setting for vq resize (ethtool -G) where vq_reset happens.
>>
>> [1] https://lists.oasis-open.org/archives/virtio-dev/202303/msg00415.html
>>
>> Fixes: 394bd87764b6 ("virtio_net: support per queue interrupt coalesce command")
> I'm not sure this is a real fix as spec allows it to go zero?

The spec says that if the user has configured interrupt coalescing 
parameters,
parameters need to be restored after vq_reset, otherwise set to 0.
vi->intr_coal_tx and vi->intr_coal_rx always save the newest global 
parameters,
regardless of whether the command is sent or not. So I think we need 
this patch
it complies with the specification requirements.

Thanks!

>
> Thanks