From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:40506) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hAxF1-0004fE-8x for qemu-devel@nongnu.org; Mon, 01 Apr 2019 09:44:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hAxF0-0000OB-44 for qemu-devel@nongnu.org; Mon, 01 Apr 2019 09:44:47 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:41605) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hAxEz-0000MY-Eh for qemu-devel@nongnu.org; Mon, 01 Apr 2019 09:44:45 -0400 Received: by mail-qt1-f196.google.com with SMTP id w30so10554386qta.8 for ; Mon, 01 Apr 2019 06:44:44 -0700 (PDT) Date: Mon, 1 Apr 2019 09:44:40 -0400 From: "Michael S. Tsirkin" Message-ID: <20190401093414-mutt-send-email-mst@kernel.org> References: <20190325035613.18192-1-jasowang@redhat.com> <20190325074939-mutt-send-email-mst@kernel.org> <92955c79-8389-85d5-cc1a-545c35aceb74@redhat.com> <20190326084809-mutt-send-email-mst@kernel.org> <54169022-3b92-a49b-88b9-076e64a22e10@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54169022-3b92-a49b-88b9-076e64a22e10@redhat.com> Subject: Re: [Qemu-devel] [PATCH V2 RFT] vhost_net: don't set backend for the uninitialized virtqueue List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: yuri.benditovich@daynix.com, qemu-devel@nongnu.org On Wed, Mar 27, 2019 at 10:27:01AM +0800, Jason Wang wrote: > > On 2019/3/26 下午8:49, Michael S. Tsirkin wrote: > > On Tue, Mar 26, 2019 at 02:59:19PM +0800, Jason Wang wrote: > > > On 2019/3/25 下午8:32, Michael S. Tsirkin wrote: > > > > On Mon, Mar 25, 2019 at 11:56:13AM +0800, Jason Wang wrote: > > > > > We used to set backend unconditionally, this won't work for some > > > > > guests (e.g windows driver) who may not initialize all virtqueues. For > > > > > kernel backend, this will fail since it may try to validate the rings > > > > > during setting backend. > > > > > > > > > > Fixing this by simply skipping the backend set when we find desc is > > > > > not ready. > > > > > > > > > > Signed-off-by: Jason Wang > > > > > --- > > > > > hw/net/vhost_net.c | 15 +++++++++++++++ > > > > > 1 file changed, 15 insertions(+) > > > > > > > > > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > > > > > index be3cc88370..04fd924d15 100644 > > > > > --- a/hw/net/vhost_net.c > > > > > +++ b/hw/net/vhost_net.c > > > > > @@ -221,6 +221,7 @@ static int vhost_net_start_one(struct vhost_net *net, > > > > > VirtIODevice *dev) > > > > > { > > > > > struct vhost_vring_file file = { }; > > > > > + hwaddr a; > > > > > int r; > > > > > net->dev.nvqs = 2; > > > > > @@ -244,6 +245,13 @@ static int vhost_net_start_one(struct vhost_net *net, > > > > > qemu_set_fd_handler(net->backend, NULL, NULL, NULL); > > > > > file.fd = net->backend; > > > > > for (file.index = 0; file.index < net->dev.nvqs; ++file.index) { > > > > > + a = virtio_queue_get_desc_addr(dev, > > > > > + net->dev.vq_index + > > > > > + file.index); > > > > > + if (a == 0) { > > > > > + /* Queue might not be ready for start */ > > > > > + continue; > > > > > + } > > > > > r = vhost_net_set_backend(&net->dev, &file); > > > > > if (r < 0) { > > > > > r = -errno; > > > > > @@ -256,6 +264,13 @@ fail: > > > > > file.fd = -1; > > > > > if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) { > > > > > while (file.index-- > 0) { > > > > > + a = virtio_queue_get_desc_addr(dev, > > > > > + net->dev.vq_index + > > > > > + file.index); > > > > > + if (a == 0) { > > > > > + /* Queue might not be ready for start */ > > > > > + continue; > > > > > + } > > > > > int r = vhost_net_set_backend(&net->dev, &file); > > > > > assert(r >= 0); > > > > > } > > > > I think we want an API that explicitly says "queue is enabled". > > > > For 0.X it will return !!addr. For 1.X it will return enabled. > > > For 1.x, desc.addr won't be set until queue_enabled is set through > > > virtio_queue_set_vrings(). And it looks to me ccw did something similar of > > > CMD_SET_VQ. > > > > > > So we're ok actually? > > > > > > Thanks > > > > > OK maybe but why can't we use an explicit API? > > 0.X can use addr != 0 trick since there's no queue_enabled. > > > > If I understand correctly, you want something similar to what V1 did? A bus > specific queue_enable() method. > > Thanks For now all I am asking for is simply: virtio_queue_is_enabled() { /* desc is only set when queue is enabled */ return vdev->vq[n].vring.desc != 0; } and then we can look at moving the enabled flag into struct VRing longer term. -- MST