From patchwork Fri Jan 20 08:17:08 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Wang X-Patchwork-Id: 136955 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 7371FB6EF2 for ; Fri, 20 Jan 2012 19:22:09 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752540Ab2ATIVd (ORCPT ); Fri, 20 Jan 2012 03:21:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46287 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752368Ab2ATIVC (ORCPT ); Fri, 20 Jan 2012 03:21:02 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q0K8KxL9032291 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 20 Jan 2012 03:21:00 -0500 Received: from amd-6168-8-1.englab.nay.redhat.com (amd-6168-8-1.englab.nay.redhat.com [10.66.104.52]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q0K8KutU006813; Fri, 20 Jan 2012 03:20:57 -0500 Subject: [PATCH 2/2] virtio: correct the memory barrier in virtqueue_kick_prepare() To: rusty@rustcorp.com.au, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, mst@redhat.com From: Jason Wang Cc: netdev@vger.kernel.org, kvm@vger.kernel.org Date: Fri, 20 Jan 2012 16:17:08 +0800 Message-ID: <20120120081708.50747.60241.stgit@amd-6168-8-1.englab.nay.redhat.com> In-Reply-To: <20120120081658.50747.10625.stgit@amd-6168-8-1.englab.nay.redhat.com> References: <20120120081658.50747.10625.stgit@amd-6168-8-1.englab.nay.redhat.com> User-Agent: StGit/3.1-rc9-1929-g8b3408 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Use virtio_mb() to make sure the available index to be exposed before checking the the avail event. Otherwise we may get stale value of avail event in guest and never kick the host after. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin --- drivers/virtio/virtio_ring.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 78428a8..07d9360 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -308,9 +308,9 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq) bool needs_kick; START_USE(vq); - /* Descriptors and available array need to be set before we expose the - * new available array entries. */ - virtio_wmb(vq); + /* We need expose available array entries before checking avail + * event. */ + virtio_mb(vq); old = vq->vring.avail->idx - vq->num_added; new = vq->vring.avail->idx;