Subject: Re: [PATCH] hv_netvsc: Fix net device attach on older Windows hosts

From: Mohammed Gamal <[email-masked]>
Date: Tue, 08 May 2018 20:17:51 +0200

On Tue, 2018-05-08 at 11:13 -0700, Stephen Hemminger wrote:
> On Tue,  8 May 2018 19:40:47 +0200
> Mohammed Gamal <[email-masked]> wrote:
> 
> > On older windows hosts the net_device instance is returned to
> > the caller of rndis_filter_device_add() without having the presence
> > bit set first. This would cause any subsequent calls to network
> > device
> > operations (e.g. MTU change, channel change) to fail after the
> > device
> > is detached once, returning -ENODEV.
> > 
> > Make sure we explicitly call netif_device_attach() before returning
> > the net_device instance to make sure the presence bit is set
> > 
> > Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
> > 
> > Signed-off-by: Mohammed Gamal <[email-masked]>
> > ---
> >  drivers/net/hyperv/rndis_filter.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/hyperv/rndis_filter.c
> > b/drivers/net/hyperv/rndis_filter.c
> > index 6b127be..09a3c1d 100644
> > --- a/drivers/net/hyperv/rndis_filter.c
> > +++ b/drivers/net/hyperv/rndis_filter.c
> > @@ -1287,8 +1287,10 @@ struct netvsc_device
> > *rndis_filter_device_add(struct hv_device *dev,
> >  		   rndis_device->hw_mac_adr,
> >  		   rndis_device->link_state ? "down" : "up");
> >  
> > -	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5)
> > +	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5) {
> > +		netif_device_attach(net);
> >  		return net_device;
> > +	}
> 
> Yes, this looks right, but it might be easier to use goto existing
> exit
> path.
> 

I was just not sure if we should set max_chn and num_chn here. I will
modify the patch and resend.

> diff --git a/drivers/net/hyperv/rndis_filter.c
> b/drivers/net/hyperv/rndis_filter.c
> index 3b6dbacaf77d..ed941c5a0be9 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -1316,7 +1316,7 @@ struct netvsc_device
> *rndis_filter_device_add(struct hv_device *dev,
>                    rndis_device->link_state ? "down" : "up");
>  
>         if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5)
> -               return net_device;
> +               goto out;
>  
>         rndis_filter_query_link_speed(rndis_device, net_device);
>