[virtio-comment] Re: [virtio-dev] [PATCH v14] virtio-net: support the virtqueue coalescing moderation

From: Heng Qi <hengqi@linux.alibaba.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: virtio-dev@lists.oasis-open.org,
	virtio-comment@lists.oasis-open.org,
	Cornelia Huck <cohuck@redhat.com>,
	Parav Pandit <parav@nvidia.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Alvaro Karsz <alvaro.karsz@solid-run.com>,
	David Edmondson <david.edmondson@oracle.com>,
	Jason Wang <jasowang@redhat.com>,
	Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Subject: [virtio-comment] Re: [virtio-dev] [PATCH v14] virtio-net: support the virtqueue coalescing moderation
Date: Mon, 10 Apr 2023 21:33:54 +0800	[thread overview]
Message-ID: <8a08b4ee-3b9a-86a0-6c42-b227a971e815@linux.alibaba.com> (raw)
In-Reply-To: <20230404182925.349d402e.pasic@linux.ibm.com>

在 2023/4/5 上午12:29, Halil Pasic 写道:
> On Thu, 23 Mar 2023 23:24:22 +0800
> Heng Qi <hengqi@linux.alibaba.com> wrote:
>
>> +struct virtio_net_ctrl_coal_vq {
>> +    le16 vqn;
>> +    le16 reserved;
>> +    struct virtio_net_ctrl_coal coal;
>> +};
>> +
>>   #define VIRTIO_NET_CTRL_NOTF_COAL 6
>>    #define VIRTIO_NET_CTRL_NOTF_COAL_TX_SET  0
>>    #define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET 1
>> + #define VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET 2
>> + #define VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET 3
>>   \end{lstlisting}
>>   
>>   Coalescing parameters:
>>   \begin{itemize}
>> +\item \field{vqn}: The virtqueue number of an enabled transmit or receive virtqueue.
> Just to be on the safe side: VIRTIO_F_NOTIF_CONFIG_DATA has been
> negotiated, and queue_select != queue_notify_data, is vqn supposed
> to contain queue_notify_data or the number/index that is used for
> queue_select (I'm talking about the PCI transport case)?

Queue event notification is based on transport, as we know, this should 
be discussed in the virtio transport chapter.
Virtqueue coalescing moderation uses the same vqn field as 
notifications, but this has a completely different meaning.
For example, when VIRTIO_F_NOTIF_CONFIG_DATA is negotiated, vqn uses the 
identifier (which Parav is doing) represented by q_notify_data,
such as virtqueue index/number or offset, etc.
vqn here does not belong to the PCI configuration space, because now we 
have involved controlq, which is used to set the non-configuration space.

Thanks.

>
> Regards,
> Halil

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