From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46439) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnSU5-00026T-83 for qemu-devel@nongnu.org; Fri, 23 Sep 2016 11:33:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bnSU1-0004tU-37 for qemu-devel@nongnu.org; Fri, 23 Sep 2016 11:33:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57284) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnSU0-0004tI-TU for qemu-devel@nongnu.org; Fri, 23 Sep 2016 11:33:49 -0400 Date: Fri, 23 Sep 2016 18:33:47 +0300 From: "Michael S. Tsirkin" Message-ID: <20160923183214-mutt-send-email-mst@kernel.org> References: <1474625046-19127-1-git-send-email-chen_han_xiao@126.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1474625046-19127-1-git-send-email-chen_han_xiao@126.com> Subject: Re: [Qemu-devel] [PATCH v2] vhost_net: don't enable vring if backend lack this feature List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Chen Hanxiao Cc: qemu-devel@nongnu.org, Jason Wang , Chen Hanxiao On Fri, Sep 23, 2016 at 06:04:06PM +0800, Chen Hanxiao wrote: > From: Chen Hanxiao > > If backend(such as dpdk) lack the feather, Sorry, I don't understand what does this mean. > don't assume it in vring_enable. > Or we may fail in vhost_net_start, then we can't use vhost. > This will bring compat issue with old version backend. > > Signed-off-by: Chen Hanxiao > --- > v2: return 0 there if protocol features aren't negotiated. > > hw/net/vhost_net.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > index f2d49ad..a1b796a 100644 > --- a/hw/net/vhost_net.c > +++ b/hw/net/vhost_net.c > @@ -425,11 +425,17 @@ int vhost_set_vring_enable(NetClientState *nc, int enable) > { > VHostNetState *net = get_vhost_net(nc); > const VhostOps *vhost_ops = net->dev.vhost_ops; > - > - nc->vring_enable = enable; > + int ret; > > if (vhost_ops && vhost_ops->vhost_set_vring_enable) { > - return vhost_ops->vhost_set_vring_enable(&net->dev, enable); > + ret = vhost_ops->vhost_set_vring_enable(&net->dev, enable); > + /* > + * Try to enable vring feature. What does this mean? > + * If protocol features aren't negotiated, return 0 for back compat. How do you mean "for back compat"? > + */ > + if (ret == 0) { > + nc->vring_enable = enable; > + } > } This clearly does not set vring_enable if vhost_set_vring_enable is NULL. > > return 0; > -- > 1.8.3.1 >