From mboxrd@z Thu Jan  1 00:00:00 1970
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Subject: Re: [PATCH v2 4/7] vhost: translate iovas at vectors
	fill time
Date: Wed, 27 Jun 2018 10:38:53 +0200
Message-ID: <4bc109b3-99f3-2266-e672-444c59c2fdbb@redhat.com>
References: <20180623071127.22999-1-maxime.coquelin@redhat.com>
 <20180623071127.22999-5-maxime.coquelin@redhat.com>
 <20180625022143.GA19607@debian>
 <45538e52-174b-7608-5320-f4ff06afc250@redhat.com>
 <20180625103124.GA16690@debian>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Cc: zhihong.wang@intel.com, dev@dpdk.org
To: Tiwei Bie <tiwei.bie@intel.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mx1.redhat.com (mx3-rdu2.redhat.com [66.187.233.73])
 by dpdk.org (Postfix) with ESMTP id 296751B5F6
 for <dev@dpdk.org>; Wed, 27 Jun 2018 10:38:56 +0200 (CEST)
In-Reply-To: <20180625103124.GA16690@debian>
Content-Language: en-US
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>



On 06/25/2018 12:31 PM, Tiwei Bie wrote:
> On Mon, Jun 25, 2018 at 09:19:34AM +0200, Maxime Coquelin wrote:
>> On 06/25/2018 04:21 AM, Tiwei Bie wrote:
>>> On Sat, Jun 23, 2018 at 09:11:24AM +0200, Maxime Coquelin wrote:
> [...]
>>>> @@ -293,7 +314,8 @@ fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
>>>>    static inline int
>>>>    reserve_avail_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
>>>>    				uint32_t size, struct buf_vector *buf_vec,
>>>> -				uint16_t *num_buffers, uint16_t avail_head)
>>>> +				uint16_t *num_buffers, uint16_t avail_head,
>>>> +				uint16_t *nr_vec)
>>>>    {
>>>>    	uint16_t cur_idx;
>>>>    	uint32_t vec_idx = 0;
>>>> @@ -315,7 +337,8 @@ reserve_avail_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
>>>>    			return -1;
>>>>    		if (unlikely(fill_vec_buf(dev, vq, cur_idx, &vec_idx, buf_vec,
>>>> -						&head_idx, &len) < 0))
>>>> +						&head_idx, &len,
>>>> +						VHOST_ACCESS_RO) < 0))
>>>
>>> reserve_avail_buf() is called by virtio_dev_rx(),
>>> so the write perm is needed.
>> Right.
>>
>> To avoid having to pass the perms, I wonder if it wouldn't be better to
>> rely on the descriptors' VRING_DESC_F_WRITE flag.
>>
> 
> Currently, DPDK vhost net doesn't check this flag,
> so it could cause problems in some cases. If we
> want to rely on this flag, I think we still need
> to pass something similar to tell fill_vec_buf()
> whether the bufs will be written or read, so the
> flag can be checked.

Right, let's keep the perm parameter for now.

Thanks,
Maxime

> Best regards,
> Tiwei Bie
>