From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org, zhihong.wang@intel.com, lining18@jd.com
Subject: Re: [dpdk-dev] [PATCH 2/3] net/virtio_user: fix wrong sequence of messages
Date: Thu, 8 Sep 2016 16:53:22 +0800 [thread overview]
Message-ID: <53e1d78c-e3b0-e16c-992d-e45ed1b31a4f@intel.com> (raw)
In-Reply-To: <20160906082011.GA23158@yliu-dev.sh.intel.com>
On 9/6/2016 4:20 PM, Yuanhan Liu wrote:
> On Tue, Sep 06, 2016 at 03:54:30PM +0800, Tan, Jianfeng wrote:
>> Hi Yuanhan,
>>
>>
>> On 9/6/2016 2:42 PM, Yuanhan Liu wrote:
>>> On Fri, Aug 05, 2016 at 11:36:42AM +0000, Jianfeng Tan wrote:
>>>> When virtio_user is used with VPP's native vhost user, it cannot
>>>> send/receive any packets.
>>>>
>>>> The root cause is that vpp-vhost-user translates the message
>>>> VHOST_USER_SET_FEATURES as puting this device into init state,
>>>> aka, zero all related structures. However, previous code
>>>> puts this message at last in the whole initialization process,
>>>> which leads to all previous information are zeroed.
>>>>
>>>> To fix this issue, we rearrange the sequence of those messages.
>>>> - step 0, send VHOST_USER_SET_VRING_CALL so that vhost allocates
>>>> virtqueue structures;
>>> Yes, it is. However, it's not that right to do that (you see there is
>>> a FIXME in vhost_user_set_vring_call()).
>> I suppose you are specifying vhost_set_vring_call().
> Oh, I was talking about the new code: I have renamed it to
> vhost_user_set_vring_call :)
>
>>> That means it need be fixed: we should not rely on fact that it's the
>>> first per-vring message we will get in the current QEMU implementation
>>> as the truth.
>>>
>>> That also means, naming a function like virtio_user_create_queue() based
>>> on above behaviour is wrong.
>> It's actually a good catch. After a light thought, I think in DPDK vhost, we
>> may need to create those virtqueues once unix socket gets connected, just
>> like in vhost-net, virtqueues are created on char file open. Right?
> There is a difference: for vhost-net and tap mode, IIRC, it knows how
> many queues before doing setup.
No, from linux/drivers/vhost/net.c:vhost_net_open(), we can see that
virtqueues are allocated according to VHOST_NET_VQ_MAX.
How about reconsidering previous suggestion to allocate vq once
connection is established?
Never mind, above fix on the vhost side will not take effect on existing
vpp-vhost implementations. We still need to fix it in the virtio side.
> While for vhost-user, it doesn't. That
> means, we have to allocate and setup virtqueues reactively: just like
> what we have done in vhost_set_vring_call(). What doesn't look perfect
> is it assume SET_VRING_CALL is the first per-vring message we will get.
Yes, depending on the assumption that SET_VRING_CALL is the first
per-vring message, looks like a bad implementation. As Stephen has
suggested, it's more like a bug in vpp. If we treat it like that way, we
will fix nothing here.
>>>> - step 1, send VHOST_USER_SET_FEATURES to confirm the features;
>>>> - step 2, send VHOST_USER_SET_MEM_TABLE to share mem regions;
>>>> - step 3, send VHOST_USER_SET_VRING_NUM, VHOST_USER_SET_VRING_BASE,
>>>> VHOST_USER_SET_VRING_ADDR, VHOST_USER_SET_VRING_KICK for each
>>>> queue;
>>>> - ...
>>>>
>>>> Fixes: 37a7eb2ae816 ("net/virtio-user: add device emulation layer")
>>>>
>>>> Reported-by: Zhihong Wang <zhihong.wang@intel.com>
>>>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>>>> ---
>>>> drivers/net/virtio/virtio_user/virtio_user_dev.c | 120 ++++++++++++++---------
>>>> 1 file changed, 72 insertions(+), 48 deletions(-)
>>> That's too much of code for a bug fix. I'm wondering how about just
>>> moving VHOST_USER_GET_PROTOCOL_FEATURES ahead, to the begining of
>>> virtio_user_start_device()? It should fix this issue.
>> Why does VHOST_USER_GET_PROTOCOL_FEATURES care? Do you mean shifting
>> VHOST_USER_SET_FEATURES earlier?
> Oops, right, I meant SET_FEATURES. Sorry about confusion introduced by
> the silly auto-completion.
Still not working. VPP needs SET_VRING_CALL to create vq firstly.
Thanks,
Jianfeng
>
> --yliu
next prev parent reply other threads:[~2016-09-08 8:53 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-05 11:36 [dpdk-dev] [PATCH 0/3] fix virtio_user issues Jianfeng Tan
2016-08-05 11:36 ` [dpdk-dev] [PATCH 1/3] net/virtio_user: fix queue pair not enabled Jianfeng Tan
2016-09-06 6:30 ` Yuanhan Liu
2016-08-05 11:36 ` [dpdk-dev] [PATCH 2/3] net/virtio_user: fix wrong sequence of messages Jianfeng Tan
2016-08-05 16:36 ` Stephen Hemminger
2016-08-08 1:19 ` Tan, Jianfeng
2016-09-06 6:42 ` Yuanhan Liu
2016-09-06 7:54 ` Tan, Jianfeng
2016-09-06 8:20 ` Yuanhan Liu
2016-09-08 8:53 ` Tan, Jianfeng [this message]
2016-09-08 12:18 ` Yuanhan Liu
2016-09-09 3:59 ` Tan, Jianfeng
2016-09-09 4:19 ` Yuanhan Liu
2016-09-09 5:50 ` Tan, Jianfeng
2016-09-09 6:03 ` Yuanhan Liu
2016-09-09 6:24 ` Tan, Jianfeng
2016-09-09 6:31 ` Yuanhan Liu
2016-08-05 11:36 ` [dpdk-dev] [PATCH 3/3] net/virtio_user: fix dev not freed after init error Jianfeng Tan
2016-08-05 16:34 ` Stephen Hemminger
2016-08-08 1:07 ` Tan, Jianfeng
2016-08-29 7:01 ` [dpdk-dev] [PATCH 0/3] fix virtio_user issues Christian Ehrhardt
2016-09-27 19:11 ` [dpdk-dev] [PATCH v2 " Jianfeng Tan
2016-09-27 19:11 ` [dpdk-dev] [PATCH v2 1/3] net/virtio_user: fix queue pair not enabled Jianfeng Tan
2016-09-28 0:05 ` Yuanhan Liu
2016-09-27 19:11 ` [dpdk-dev] [PATCH v2 2/3] net/virtio_user: fix wrong sequence of messages Jianfeng Tan
2016-09-27 19:11 ` [dpdk-dev] [PATCH v2 3/3] net/virtio_user: fix dev not freed after init error Jianfeng Tan
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