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. 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.
>
> >
> >> - 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.
--yliu
