Re: [RFC PATCH 1/2] hv_netvsc: Split netvsc_revoke_buf() and netvsc_teardown_gpadl()

[Mohammed Gamal <mgamal@redhat.com>]

On Wed, 2018-01-31 at 15:01 -0800, Stephen Hemminger wrote:
> On Wed, 31 Jan 2018 12:16:49 +0100
> Mohammed Gamal <mgamal@redhat.com> wrote:
> 
> > On Tue, 2018-01-30 at 11:29 -0800, Stephen Hemminger wrote:
> > > On Tue, 23 Jan 2018 10:34:04 +0100
> > > Mohammed Gamal <mgamal@redhat.com> wrote:
> > >   
> > > > Split each of the functions into two for each of send/recv
> > > > buffers
> > > > 
> > > > Signed-off-by: Mohammed Gamal <mgamal@redhat.com>  
> > > 
> > > Splitting these functions is not necessary  
> > 
> > How so? We need to send each message independently, and hence the
> > split
> > (see cover letter). Is there another way?
> 
> This is all that is needed.
> 
> 
> Subject: [PATCH] hv_netvsc: work around for gpadl teardown on older
> windows
>  server
> 
> On WS2012 the host ignores messages after vmbus channel is closed.
> Workaround this by doing what Windows does and send the teardown
> before close on older versions of NVSP protocol.
> 
> Reported-by: Mohammed Gamal <mgamal@redhat.com>
> Fixes: 0cf737808ae7 ("hv_netvsc: netvsc_teardown_gpadl() split")
> Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> ---
>  drivers/net/hyperv/netvsc.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/hyperv/netvsc.c
> b/drivers/net/hyperv/netvsc.c
> index 17e529af79dc..1a3df0eff42f 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -574,10 +574,17 @@ void netvsc_device_remove(struct hv_device
> *device)
>  	 */
>  	netdev_dbg(ndev, "net device safe to remove\n");
>  
> +	/* Workaround for older versions of Windows require that
> +	 * buffer be revoked before channel is disabled
> +	 */
> +	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_4)
> +		netvsc_teardown_gpadl(device, net_device);
> +
>  	/* Now, we can close the channel safely */
>  	vmbus_close(device->channel);
>  
> -	netvsc_teardown_gpadl(device, net_device);
> +	if (net_device->nvsp_version >= NVSP_PROTOCOL_VERSION_4)
> +		netvsc_teardown_gpadl(device, net_device);
>  
>  	/* And dissassociate NAPI context from device */
>  	for (i = 0; i < net_device->num_chn; i++)

I've tried a similar workaround before by calling
netvsc_teardown_gpadl() after netvsc_revoke_buf(), but before setting
net_device_ctx->nvdev to NULL and it caused the guest to hang when
trying to change MTU. 

Let me try that change and see if it behaves differently.