From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55134) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZoX32-0006oi-07 for qemu-devel@nongnu.org; Tue, 20 Oct 2015 09:33:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZoX2v-00022D-IM for qemu-devel@nongnu.org; Tue, 20 Oct 2015 09:33:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51238) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZoX2v-000225-Ct for qemu-devel@nongnu.org; Tue, 20 Oct 2015 09:33:45 -0400 Date: Tue, 20 Oct 2015 16:33:42 +0300 From: "Michael S. Tsirkin" Message-ID: <20151020163155-mutt-send-email-mst@redhat.com> References: <1445259567-28516-1-git-send-email-thibaut.collet@6wind.com> <1445259567-28516-2-git-send-email-thibaut.collet@6wind.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445259567-28516-2-git-send-email-thibaut.collet@6wind.com> Subject: Re: [Qemu-devel] [PATCH 1/1] vhost: set the correct queue index in case of migration with multiqueue List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thibaut Collet Cc: pbonzini@redhat.com, jasowang@redhat.com, marcandre.lureau@gmail.com, qemu-devel@nongnu.org, haifeng.lin@huawei.com On Mon, Oct 19, 2015 at 02:59:27PM +0200, Thibaut Collet wrote: > When a live migration is started the log address to mark dirty pages is provided > to the vhost backend through the vhost_dev_set_log function. > This function is called for each queue pairs but the queue index is wrongly set: > always set to the first queue pair. Then vhost backend lost descriptor addresses > of the queue pairs greater than 1 and behaviour of the vhost backend is > unpredictable. > > The queue index is computed by taking account of the vq_index (to retrieve the > queue pair index) and calling the vhost_get_vq_index method of the backend. > > Signed-off-by: Thibaut Collet Thanks! The code in question was added by: commit a9f98bb5ebe6fb1869321dcc58e72041ae626ad8 Author: Jason Wang Date: Wed Jan 30 19:12:35 2013 +0800 vhost: multiqueue support Jason, could you comment on whether this makes sense please? If yes - this is an old bug, and we need this on stable, do we not? Maybe we should refactor vhost_virtqueue_set_addr to make it call vhost_get_vq_index internally automatically. All callers do this anyway. This can be a patch on top. > --- > hw/virtio/vhost.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index feeaaa4..de29968 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -656,13 +656,14 @@ static int vhost_dev_set_features(struct vhost_dev *dev, bool enable_log) > > static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log) > { > - int r, t, i; > + int r, t, i, idx; > r = vhost_dev_set_features(dev, enable_log); > if (r < 0) { > goto err_features; > } > for (i = 0; i < dev->nvqs; ++i) { > - r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i, > + idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i); > + r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx, > enable_log); > if (r < 0) { > goto err_vq; > @@ -671,7 +672,8 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log) > return 0; > err_vq: > for (; i >= 0; --i) { > - t = vhost_virtqueue_set_addr(dev, dev->vqs + i, i, > + idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i); > + t = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx, > dev->log_enabled); > assert(t >= 0); > } > -- > 2.1.4