Re: [dpdk-dev] [PATCH 27/40] net/virtio: add Virtio-user memory tables ops

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 1/6/21 12:57 PM, Xia, Chenbo wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Monday, December 21, 2020 5:14 AM
>> To: dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; olivier.matz@6wind.com;
>> amorenoz@redhat.com; david.marchand@redhat.com
>> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Subject: [PATCH 27/40] net/virtio: add Virtio-user memory tables ops
>>
>> This patch implements a dedicated callback for
>> preparing and sending memory table to the backends.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
> 
> <snip>
> 
>>
>> +static int
>> +vhost_user_check_reply_ack(struct virtio_user_dev *dev, struct vhost_user_msg
>> *msg)
>> +{
>> +	enum vhost_user_request req = msg->request;
>> +	int ret;
>> +
>> +	if (!(msg->flags & VHOST_USER_NEED_REPLY_MASK))
>> +		return 0;
>> +
>> +	ret = vhost_user_read(dev->vhostfd, msg);
>> +	if (ret < 0) {
>> +		PMD_DRV_LOG(ERR, "Failed to read reply-ack");
>> +		return -1;
>> +	}
>> +
>> +	if (req != msg->request) {
>> +		PMD_DRV_LOG(ERR, "Unexpected reply-ack request type (%d)", msg-
>>> request);
>> +		return -1;
>> +	}
> 
> I think it's better to keep the size check: msg.size should equal sizeof(msg.payload.u64).
> 
>> +
>> +	return msg->payload.u64 ? -1 : 0;
> 
> I think it's better to add a log after checking payload's value. Looking back to
> vhost_user_set_memory_table, there's no way for user or developer to know what has
> failed (vhost_user_write fails or NACK). Maybe it's also better to add error log in
> or outside vhost_user_write :)

Indeed, we are lacking logs here, I added both a log when slave replies
NACK and when sendmsg fails.

Thanks,
Maxime

> Thanks,
> Chenbo
>