Hi On Wed, May 3, 2017 at 7:09 AM Yang, Zhiyong <zhiyong.y...@intel.com> wrote:
> Hi,Maxime: > > > -----Original Message----- > > From: Maxime Coquelin [mailto:maxime.coque...@redhat.com] > > Sent: Tuesday, May 2, 2017 8:23 PM > > To: Yang, Zhiyong <zhiyong.y...@intel.com>; qemu-devel@nongnu.org > > Cc: m...@redhat.com > > Subject: Re: [Qemu-devel] [PATCH] hw/virtio: fix vhost user fails to > startup when > > MQ > > > > > > > > On 04/28/2017 09:09 AM, Zhiyong Yang wrote: > > > Qemu2.7~2.9 and vhost user for dpdk 17.02 release work together to > > > cause failures of new connection when negotiating to set MQ. > > > (one queue pair works well). > > > Because there exist some bugs in qemu code when introducing > > > VHOST_USER_PROTOCOL_F_REPLY_ACK to qemu. When > > vhost_user_set_mem_table > > > is invoked to deal with the vhost message VHOST_USER_SET_MEM_TABLE for > > > the second time, qemu indeed doesn't send the messge (The message > > > needs to be sent only once)but still will be waiting for dpdk's reply > > > ack, then, qemu is always freezing, while DPDK is always waiting for > > > next vhost message from qemu. > > > The patch aims to fix the bug, MQ can work well. > > > The same bug is found in function vhost_user_net_set_mtu, it is > > > fixed at the same time. > > > DPDK related patch is as following: > > > http://www.dpdk.org/dev/patchwork/patch/23955/ > > > > > > Signed-off-by: Zhiyong Yang <zhiyong.y...@intel.com> > > > --- > > > hw/virtio/vhost-user.c | 18 +++++++++++------- > > > 1 file changed, 11 insertions(+), 7 deletions(-) > > > > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index > > > 9334a8a..c2c54ce 100644 > > > --- a/hw/virtio/vhost-user.c > > > +++ b/hw/virtio/vhost-user.c > > > @@ -205,10 +205,11 @@ static int vhost_user_write(struct vhost_dev > *dev, > > VhostUserMsg *msg, > > > /* > > > * For non-vring specific requests, like > VHOST_USER_SET_MEM_TABLE, > > > * we just need send it once in the first time. For later such > > > - * request, we just ignore it. > > > + * request, we just ignore it. In this case, return value is 1 > which is > > > + * different from 0 that stands for message written successfully. > > > */ > > > if (vhost_user_one_time_request(msg->request) && dev->vq_index > != 0) { > > > - return 0; > > > + return 1; > > > > I personally prefer the fix I suggested in the DPDK mail thread, as > returning a > > random positive value does look like a workaround: > > I think that for vhost_user_write(), it's behaving in a different way for > some specific vhost messages. > So, it should not return the same returen value 0 which stands for success. > But you need to do the special handling for every caller. > > > > " > > I think the problem must be fixed generally and not per request. > > Maybe in vhost_user_write() if one-time request, just clear the > > VHOST_USER_NEED_REPLY flag. Then, in process_message_reply(), return > early > > if this flag isn't set. > > " > It's another choise. Either this one nor that one, not a big deal. :) > Fixing these existing bugs is the most important. > > While the suggestion from Maxime would work transparently, similar to one-time request are transparent to caller today. I also prefer that solution. thanks -- Marc-André Lureau