RE: [PATCH net-next,1/2] hv_netvsc: Fix the return status in RX path

[Haiyang Zhang]

> -----Original Message-----
> From: Michael Kelley (EOSG)
> Sent: Saturday, March 24, 2018 12:48 PM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx
> Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; vkuznets@xxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH net-next,1/2] hv_netvsc: Fix the return status in RX path
> 
> > -----Original Message-----
> > From: linux-kernel-owner@xxxxxxxxxxxxxxx
> > <linux-kernel-owner@xxxxxxxxxxxxxxx> On Behalf Of Haiyang Zhang
> > Sent: Thursday, March 22, 2018 12:01 PM
> > To: davem@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> > Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan
> > <kys@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>;
> > olaf@xxxxxxxxx; vkuznets@xxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx
> > Subject: [PATCH net-next,1/2] hv_netvsc: Fix the return status in RX
> > path
> >
> > From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> >
> > As defined in hyperv_net.h, the NVSP_STAT_SUCCESS is one not zero.
> > Some functions returns 0 when it actually means NVSP_STAT_SUCCESS.
> > This patch fixes them.
> >
> > In netvsc_receive(), it puts the last RNDIS packet's receive status
> > for all packets in a vmxferpage which may contain multiple RNDIS
> > packets.
> > This patch puts NVSP_STAT_FAIL in the receive completion if one of the
> > packets in a vmxferpage fails.
> 
> This patch changes the status field that is being reported back to the Hyper-V
> host in the receive completion message in
> enq_receive_complete().   The current code reports 0 on success,
> and with the patch, it will report 1 on success.  So does this change affect
> anything on the Hyper-V side?  Or is Hyper-V just ignoring
> the value?   If this change doesn't have any impact on the
> interactions with Hyper-V, perhaps it would be good to explain why in the
> commit message.

Here is the definition of each status code for NetVSP. 
enum {
        NVSP_STAT_NONE = 0,
        NVSP_STAT_SUCCESS,
        NVSP_STAT_FAIL,
        NVSP_STAT_PROTOCOL_TOO_NEW,
        NVSP_STAT_PROTOCOL_TOO_OLD,
        NVSP_STAT_INVALID_RNDIS_PKT,
        NVSP_STAT_BUSY,
        NVSP_STAT_PROTOCOL_UNSUPPORTED,
        NVSP_STAT_MAX,
};

Existing code returns NVSP_STAT_NONE = 0, and with this patch
we return NVSP_STAT_SUCCESS = 1. 
Based on testing, either way works for now. But for correctness
and future stability (e.g. host side becomes more stringent), we
should follow the protocol.

Thanks,
- Haiyang