From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by dpdk.org (Postfix) with ESMTP id A4E0B1E2B for ; Thu, 13 Apr 2017 04:24:25 +0200 (CEST) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP; 12 Apr 2017 19:24:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,192,1488873600"; d="scan'208";a="1134734485" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.67.162]) by fmsmga001.fm.intel.com with ESMTP; 12 Apr 2017 19:24:21 -0700 Date: Thu, 13 Apr 2017 10:21:28 +0800 From: Yuanhan Liu To: "Tan, Jianfeng" Cc: dev@dpdk.org, Maxime Coquelin Message-ID: <20170413022128.GG7333@yliu-dev.sh.intel.com> References: <1491551860-15005-1-git-send-email-jianfeng.tan@intel.com> <20170413015812.GE7333@yliu-dev.sh.intel.com> <5e7b5876-0f98-9c42-965e-e91b318cd17f@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e7b5876-0f98-9c42-965e-e91b318cd17f@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Subject: Re: [dpdk-dev] [PATCH] net/virtio-user: fix cannot get initialized X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Apr 2017 02:24:26 -0000 On Thu, Apr 13, 2017 at 10:18:43AM +0800, Tan, Jianfeng wrote: > > > On 4/13/2017 9:58 AM, Yuanhan Liu wrote: > >On Fri, Apr 07, 2017 at 07:57:40AM +0000, Jianfeng Tan wrote: > >>After the introduction of vhost MTU, VIRTIO_NET_F_MTU is enabled > >>by default. However, virtio-user vtpci does not support to get > >>MTU from device yet, i.e., vtpci_read_dev_config(MTU) fails. > >>Plus, struct virtio_net_config is defined as a uninitialized > >>variable, and could be different values in > >>virtio_negotiate_features() and virtio_init_device(). > >> > >>In some cases, it passes the check in virtio_negotiate_features() > >>but fails the check in virtio_init_device(). As a result, > >>virtio-user canno be initialized. > >> > >>To fix it, (1) accessing uninitialized variable is not a good > >>practice, so initialize it as zero; (2) explicitly disable MTU > >>feature in virtio-user. > >> > >>Fixes: 49d26d9e3f47 ("net/virtio: support MTU feature") > >>Cc: Maxime Coquelin > >>Cc: Yuanhan Liu > >> > >>Signed-off-by: Jianfeng Tan > >>--- > >> drivers/net/virtio/virtio_ethdev.c | 4 ++-- > >> drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 ++++++ > >> 2 files changed, 8 insertions(+), 2 deletions(-) > >> > >>diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c > >>index 78cb3e8..4c43784 100644 > >>--- a/drivers/net/virtio/virtio_ethdev.c > >>+++ b/drivers/net/virtio/virtio_ethdev.c > >>@@ -1163,7 +1163,7 @@ virtio_negotiate_features(struct virtio_hw *hw, uint64_t req_features) > >> /* If supported, ensure MTU value is valid before acknowledging it. */ > >> if (host_features & req_features & (1ULL << VIRTIO_NET_F_MTU)) { > >>- struct virtio_net_config config; > >>+ struct virtio_net_config config = {0}; > >virtio-user does not support the MTU feature, this patch should not be > >reached. The virtio-user feature negotiation should be broken. > > > > --yliu > > > > Yes, it will not come to here anyway. But some static code analyzer might > report this as an error: there's chance to read uninitialized variable. If so, fix it in another patch, with the detailed (and real) errors in the commit log. --yliu