Re: [dpdk-dev] [PATCH v2] examples/vhost: workaround qemu abort

["Liu, Yong" <yong.liu@intel.com>]

> -----Original Message-----
> From: Bie, Tiwei
> Sent: Wednesday, July 25, 2018 10:19 AM
> To: Liu, Yong <yong.liu@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [PATCH v2] examples/vhost: workaround qemu abort
> 
> On Wed, Jul 25, 2018 at 05:56:54PM +0800, Marvin Liu wrote:
> > Current qemu vhost net ring start has a dependency on feature bit
> > VHOST_USER_F_PROTOCOL_FEATURES. If vhost device start without it, stop
> > action will be skipped. Consequently, same ioevent fd will be added
> > twice after reloading driver and then cause qemu abort. However, ring
> > should be initialized in an enabled state when this feature bit not
> > negotiated. Work around qemu issue by enabling this feature bit in vhost
> > user backend.
> >
> > Signed-off-by: Marvin Liu <yong.liu@intel.com>
> >
> > diff --git a/examples/vhost/main.c b/examples/vhost/main.c
> > index 2175c1186..4b87331fc 100644
> > --- a/examples/vhost/main.c
> > +++ b/examples/vhost/main.c
> > @@ -1519,8 +1519,12 @@ main(int argc, char *argv[])
> >  				"vhost driver register failure.\n");
> >  		}
> >
> > -		if (builtin_net_driver)
> > +		if (builtin_net_driver) {
> >  			rte_vhost_driver_set_features(file, VIRTIO_NET_FEATURES);
> > +			/* Workaround for qemu vhost net device startup */
> > +			rte_vhost_driver_set_features(file,
> > +				1ULL << VHOST_USER_F_PROTOCOL_FEATURES);
> 
> rte_vhost_driver_set_features() will overwrite the
> existing value. You need to OR VIRTIO_NET_FEATURES
> and (1ULL << VHOST_USER_F_PROTOCOL_FEATURES).
> 
> 

Tiwei,
Thanks for point out the error, I have sent v3 for correcting this.

Regards,
Marvin
> 
> > +		}
> >
> >  		if (mergeable == 0) {
> >  			rte_vhost_driver_disable_features(file,
> > --
> > 2.17.0
> >