From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54580) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YUtFP-0005xV-R0 for qemu-devel@nongnu.org; Mon, 09 Mar 2015 04:41:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YUtFL-0004Vc-Rm for qemu-devel@nongnu.org; Mon, 09 Mar 2015 04:41:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60147) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YUtFL-0004VS-Ku for qemu-devel@nongnu.org; Mon, 09 Mar 2015 04:41:07 -0400 Date: Mon, 9 Mar 2015 09:41:01 +0100 From: "Michael S. Tsirkin" Message-ID: <20150309084101.GC22567@redhat.com> References: <1425754898-32707-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1425754898-32707-1-git-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH] virtio_rpmsg: set DRIVER_OK before using device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: linux-kernel@vger.kernel.org Cc: Ohad Ben-Cohen , Rusty Russell , qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org On Sat, Mar 07, 2015 at 08:06:56PM +0100, Michael S. Tsirkin wrote: > virtio spec requires that all drivers set DRIVER_OK > before using devices. While rpmsg isn't yet > included in the virtio 1 spec, previous spec versions > also required this. > > virtio rpmsg violates this rule: is calls kick > before setting DRIVER_OK. > > The fix isn't trivial since simply calling virtio_device_ready earlier > would mean we might get an interrupt in parallel with adding buffers. > > Instead, split kick out to prepare+notify calls. prepare before > virtio_device_ready - when we know we won't get interrupts. notify right > afterwards. > > Signed-off-by: Michael S. Tsirkin > --- Ohad, can you review and ack pls? > Note: compile-tested only. > > drivers/rpmsg/virtio_rpmsg_bus.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c > index 92f6af6..73354ee 100644 > --- a/drivers/rpmsg/virtio_rpmsg_bus.c > +++ b/drivers/rpmsg/virtio_rpmsg_bus.c > @@ -951,6 +951,7 @@ static int rpmsg_probe(struct virtio_device *vdev) > void *bufs_va; > int err = 0, i; > size_t total_buf_space; > + bool notify; > > vrp = kzalloc(sizeof(*vrp), GFP_KERNEL); > if (!vrp) > @@ -1030,8 +1031,22 @@ static int rpmsg_probe(struct virtio_device *vdev) > } > } > > + /* > + * Prepare to kick but don't notify yet - we can't do this before > + * device is ready. > + */ > + notify = virtqueue_kick_prepare(vrp->rvq); > + > + /* From this point on, we can notify and get callbacks. */ > + virtio_device_ready(vdev); > + > /* tell the remote processor it can start sending messages */ > - virtqueue_kick(vrp->rvq); > + /* > + * this might be concurrent with callbacks, but we are only > + * doing notify, not a full kick here, so that's ok. > + */ > + if (notify) > + virtqueue_notify(vrp->rvq); > > dev_info(&vdev->dev, "rpmsg host is online\n"); > > -- > MST