From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tiwei Bie <tiwei.bie@intel.com>
Subject: Re: [PATCH] examples/vhost: fix qemu abort
Date: Wed, 25 Jul 2018 09:23:51 +0800
Message-ID: <20180725012350.GA20566@debian>
References: <20180724151649.44490-1-yong.liu@intel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Cc: dev@dpdk.org, maxime.coquelin@redhat.com, zhihong.wang@intel.com
To: Marvin Liu <yong.liu@intel.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mga18.intel.com (mga18.intel.com [134.134.136.126])
 by dpdk.org (Postfix) with ESMTP id 81062160
 for <dev@dpdk.org>; Wed, 25 Jul 2018 03:24:10 +0200 (CEST)
Content-Disposition: inline
In-Reply-To: <20180724151649.44490-1-yong.liu@intel.com>
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

On Tue, Jul 24, 2018 at 11:16:49PM +0800, Marvin Liu wrote:
> When start vhost sample with builtin-net-driver argument, vhost feature
> bit will be zero. If VHOST_USER_F_PROTOCOL_FEATURES is not set, vhost
> net start will be failed in qemu. This occasion will cause device stop
> action was skipped. Consequently, same ioevent fd will be added second
> time after reload driver and then cause qemu abort. Add feature bit
> which has been supported by vhost library can fix this error.
> 
> Fixes: ca059fa5 ("examples/vhost: demonstrate the new generic APIs")

It's a bug in QEMU, this is a workaround in DPDK.
So there is no need to fix any commit in DPDK.

> 
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
> 
> diff --git a/examples/vhost/main.c b/examples/vhost/main.c
> index 2175c1186..44aec2f47 100644
> --- a/examples/vhost/main.c
> +++ b/examples/vhost/main.c
> @@ -1520,7 +1520,8 @@ main(int argc, char *argv[])
>  		}
>  
>  		if (builtin_net_driver)
> -			rte_vhost_driver_set_features(file, VIRTIO_NET_FEATURES);

There is no need to remove VIRTIO_NET_FEATURES
although it's defined to 0 (as it's helpful for
users to understand this example).

> +			rte_vhost_driver_set_features(file,
> +				1ULL << VHOST_USER_F_PROTOCOL_FEATURES);

It's better to add some comments that this is
a workaround and why this workaround is needed.

>  
>  		if (mergeable == 0) {
>  			rte_vhost_driver_disable_features(file,
> -- 
> 2.17.0
>