[dpdk-dev] [PATCH v5 7/9] net/virtio: support in-order Rx and Tx

[Liu, Yong]

> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Tuesday, July 03, 2018 12:57 AM
> To: Maxime Coquelin <maxime.coquelin at redhat.com>; Liu, Yong
> <yong.liu at intel.com>; Bie, Tiwei <tiwei.bie at intel.com>
> Cc: Wang, Zhihong <zhihong.wang at intel.com>; dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v5 7/9] net/virtio: support in-order Rx and
> Tx
> 
> On 7/2/2018 5:53 PM, Maxime Coquelin wrote:
> >
> >
> > On 07/02/2018 06:52 PM, Ferruh Yigit wrote:
> >> On 7/2/2018 5:41 PM, Ferruh Yigit wrote:
> >>> On 7/2/2018 2:56 PM, Marvin Liu wrote:
> >>>> IN_ORDER Rx function depends on merge-able feature. Descriptors
> >>>> allocation and free will be done in bulk.
> >>>>
> >>>> Virtio dequeue logic:
> >>>>      dequeue_burst_rx(burst mbufs)
> >>>>      for (each mbuf b) {
> >>>>              if (b need merge) {
> >>>>                      merge remained mbufs
> >>>>                      add merged mbuf to return mbufs list
> >>>>              } else {
> >>>>                      add mbuf to return mbufs list
> >>>>              }
> >>>>      }
> >>>>      if (last mbuf c need merge) {
> >>>>              dequeue_burst_rx(required mbufs)
> >>>>              merge last mbuf c
> >>>>      }
> >>>>      refill_avail_ring_bulk()
> >>>>      update_avail_ring()
> >>>>      return mbufs list
> >>>>
> >>>> IN_ORDER Tx function can support offloading features. Packets which
> >>>> matched "can_push" option will be handled by simple xmit function.
> Those
> >>>> packets can't match "can_push" will be handled by original xmit
> function
> >>>> with in-order flag.
> >>>>
> >>>> Virtio enqueue logic:
> >>>>      xmit_cleanup(used descs)
> >>>>      for (each xmit mbuf b) {
> >>>>              if (b can inorder xmit) {
> >>>>                      add mbuf b to inorder burst list
> >>>>                      continue
> >>>>              } else {
> >>>>                      xmit inorder burst list
> >>>>                      xmit mbuf b by original function
> >>>>              }
> >>>>      }
> >>>>      if (inorder burst list not empty) {
> >>>>              xmit inorder burst list
> >>>>      }
> >>>>      update_avail_ring()
> >>>>
> >>>> Signed-off-by: Marvin Liu <yong.liu at intel.com>
> >>>> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> >>>
> >>> <...>
> >>>
> >>>> @@ -150,6 +188,83 @@ virtio_xmit_cleanup(struct virtqueue *vq,
> uint16_t num)
> >>>>   	}
> >>>>   }
> >>>>
> >>>> +/* Cleanup from completed inorder transmits. */
> >>>> +static void
> >>>> +virtio_xmit_cleanup_inorder(struct virtqueue *vq, uint16_t num)
> >>>> +{
> >>>> +	uint16_t i, used_idx, desc_idx, last_idx;
> >>>
> >>>
> >>> Getting following build error [1], from code it looks like false
> positive, but
> >>> to get rid of the build error would it be OK to set initial value to
> "desc_idx"?
> >>
> >> I applied this while merging, if this is wrong please let me know, we
> can fix in
> >> next-net, Thanks.
> >
> > Looks good to me. I didn't catch it with the GCC version I use.
> 
> I didn't dig more but I also didn't get the error with regular build, the
> one
> with all DEBUGs enabled and mach=default combination gave the error, not
> sure why.
> 

Ferruh,
I didn't catch this error either. I tried three gcc versions 7.2.0, 7.3.0 and 4.8.3. 
May I know your gcc version? 

Thanks,
Marvin

> >
> > Thanks,
> > Maxime
> >
> >>>
> >>>
> >>> [1]
> >>> .../dpdk/drivers/net/virtio/virtio_rxtx.c:195:24: error: ‘desc_idx’
> may be used
> >>> uninitialized in this function [-Werror=maybe-uninitialized]
> >>>
> >>>
> >>>    uint16_t i, used_idx, desc_idx, last_idx;
> >>>
> >>>
> >>>
> >>>                          ^~~~~~~~
> >>>
> >>