[dpdk-dev] [PATCH v2] vhost: fix assuming packed ring size is a power of 2

Jiang, Cheng1 cheng1.jiang at intel.com
Mon Jul 12 08:53:13 CEST 2021


Hi Maxime,

I have noticed you changed the state this patch to Superseded.
So are you going to submit a new version of this patch?

Thanks,
Cheng

> -----Original Message-----
> From: Jiang, Cheng1
> Sent: Wednesday, July 7, 2021 7:11 PM
> To: Maxime Coquelin <maxime.coquelin at redhat.com>; dev at dpdk.org; Xia,
> Chenbo <Chenbo.Xia at intel.com>
> Cc: stable at dpdk.org
> Subject: RE: [PATCH v2] vhost: fix assuming packed ring size is a power of 2
> 
> Hi Maxime,
> 
> I have also noticed the wrong calculation here, thanks for the timely help.
> 
> Thanks,
> Cheng
> 
> > -----Original Message-----
> > From: Maxime Coquelin <maxime.coquelin at redhat.com>
> > Sent: Wednesday, July 7, 2021 6:30 PM
> > To: dev at dpdk.org; Jiang, Cheng1 <cheng1.jiang at intel.com>; Xia, Chenbo
> > <chenbo.xia at intel.com>
> > Cc: Maxime Coquelin <maxime.coquelin at redhat.com>; stable at dpdk.org
> > Subject: [PATCH v2] vhost: fix assuming packed ring size is a power of
> > 2
> >
> > Unlike split ring, packed ring does not mandate the ring size to be a
> > power of 2. So we have to use a modulo operation when wrapping ring
> index.
> >
> > Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath")
> > Cc: stable at dpdk.org
> >
> > Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> > ---
> >
> > V2: Also fix wrapping in virtio_dev_rx_async_get_info_idx which is
> > used in the packed ring data path.
> >
> >  lib/vhost/virtio_net.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > b93482587c..0de5231db7 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -1470,7 +1470,7 @@ virtio_dev_rx_async_get_info_idx(uint16_t
> > pkts_idx,
> >  	uint16_t vq_size, uint16_t n_inflight)  {
> >  	return pkts_idx > n_inflight ? (pkts_idx - n_inflight) :
> > -		(vq_size - n_inflight + pkts_idx) & (vq_size - 1);
> > +		(vq_size - n_inflight + pkts_idx) % vq_size;
> >  }
> >
> >  static __rte_always_inline void
> > @@ -2131,7 +2131,7 @@ uint16_t rte_vhost_poll_enqueue_completed(int
> > vid, uint16_t queue_id,
> >
> >  	if (vq_is_packed(dev)) {
> >  		for (i = 0; i < n_pkts_put; i++) {
> > -			from = (start_idx + i) & (vq_size - 1);
> > +			from = (start_idx + i) % vq_size;
> >  			n_buffers += pkts_info[from].nr_buffers;
> >  			pkts[i] = pkts_info[from].mbuf;
> >  		}
> > --
> > 2.31.1
> 
> 
> Acked-by: Cheng Jiang <cheng1.jiang at intel.com>


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