From patchwork Wed Sep 7 15:51:25 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 667082 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3sTnz64y7cz9s36 for ; Thu, 8 Sep 2016 01:52:18 +1000 (AEST) Received: from localhost ([::1]:41678 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhf95-0007sw-I4 for incoming@patchwork.ozlabs.org; Wed, 07 Sep 2016 11:52:15 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51630) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhf8R-0007Zw-F9 for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:51:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bhf8M-0001ES-FK for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:51:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17134) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhf8M-0001EM-AG for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:51:30 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A95298124A for ; Wed, 7 Sep 2016 15:51:28 +0000 (UTC) Received: from localhost (ovpn-112-67.ams2.redhat.com [10.36.112.67]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u87FpQRK031245; Wed, 7 Sep 2016 11:51:27 -0400 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Date: Wed, 7 Sep 2016 11:51:25 -0400 Message-Id: <1473263485-17084-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 07 Sep 2016 15:51:28 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH] virtio: zero vq->inuse in virtio_reset() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lprosek@redhat.com, Stefan Hajnoczi , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" vq->inuse must be zeroed upon device reset like most other virtqueue fields. In theory, virtio_reset() just needs assert(vq->inuse == 0) since devices must clean up in-flight requests during reset (requests cannot not be leaked!). In practice, it is difficult to achieve vq->inuse == 0 across reset because balloon, blk, 9p, etc implement various different strategies for cleaning up requests. Most devices call g_free(elem) directly without telling virtio.c that the VirtQueueElement is cleaned up. Therefore vq->inuse is not decremented during reset. This patch zeroes vq->inuse and trusts that devices are not leaking VirtQueueElements across reset. I will send a follow-up series that refactors request life-cycle across all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but this more invasive approach is not appropriate for stable trees. Signed-off-by: Stefan Hajnoczi Reviewed-by: Ladi Prosek Reviewed-by: Cornelia Huck --- hw/virtio/virtio.c | 1 + 1 file changed, 1 insertion(+) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 74c085c..e8a13a5 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -822,6 +822,7 @@ void virtio_reset(void *opaque) vdev->vq[i].signalled_used_valid = false; vdev->vq[i].notification = true; vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; + vdev->vq[i].inuse = 0; } }