Re: [PATCH] examples/vhost: fix qemu abort

[Tiwei Bie <tiwei.bie@intel.com>]

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
>