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 at intel.com> >>>> Signed-off-by: Jianfeng Tan <jianfeng.tan at 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