netdev - Re: [PATCH RFC v8 02/11] vhost: use batched get_vq

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Date:   Tue, 23 Jun 2020 10:51:34 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        eperezma@...hat.com
Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version


On 2020/6/23 上午12:00, Michael S. Tsirkin wrote:
> On Wed, Jun 17, 2020 at 11:19:26AM +0800, Jason Wang wrote:
>> On 2020/6/11 下午7:34, Michael S. Tsirkin wrote:
>>>    static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
>>>    {
>>>    	kfree(vq->descs);
>>> @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
>>>    	for (i = 0; i < dev->nvqs; ++i) {
>>>    		vq = dev->vqs[i];
>>>    		vq->max_descs = dev->iov_limit;
>>> +		if (vhost_vq_num_batch_descs(vq) < 0) {
>>> +			return -EINVAL;
>>> +		}
>> This check breaks vdpa which set iov_limit to zero. Consider iov_limit is
>> meaningless to vDPA, I wonder we can skip the test when device doesn't use
>> worker.
>>
>> Thanks
> It doesn't need iovecs at all, right?
>
> -- MST


Yes, so we may choose to bypass the iovecs as well.

Thanks