From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35009) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V8VeR-0006X3-N3 for qemu-devel@nongnu.org; Sun, 11 Aug 2013 09:25:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V8VeL-0006tS-Nu for qemu-devel@nongnu.org; Sun, 11 Aug 2013 09:25:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49671) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V8VeL-0006t4-E3 for qemu-devel@nongnu.org; Sun, 11 Aug 2013 09:25:37 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r7BDPYiu005929 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sun, 11 Aug 2013 09:25:35 -0400 From: Gal Hammer Date: Sun, 11 Aug 2013 16:25:25 +0300 Message-Id: <1376227525-28639-1-git-send-email-ghammer@redhat.com> Subject: [Qemu-devel] [PATCH v2] virtio-serial: Do not notify virtqueue if no element was pushed back. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Gal Hammer The redundant notification caused the Windows' driver to duplicate the pending write request's buffer. The driver was fixed, but I think this change is still required. Signed-off-by: Gal Hammer --- hw/char/virtio-serial-bus.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c index da417c7..0d38b4b 100644 --- a/hw/char/virtio-serial-bus.c +++ b/hw/char/virtio-serial-bus.c @@ -105,6 +105,7 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq, VirtIODevice *vdev) { VirtIOSerialPortClass *vsc; + bool elem_pushed = false; assert(port); assert(virtio_queue_ready(vq)); @@ -145,9 +146,12 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq, break; } virtqueue_push(vq, &port->elem, 0); + elem_pushed = true; port->elem.out_num = 0; } - virtio_notify(vdev, vq); + if (elem_pushed) { + virtio_notify(vdev, vq); + } } static void flush_queued_data(VirtIOSerialPort *port) -- 1.8.1.4