Re: [dpdk-dev] [PATCH] vhost: dequeue zero copy should restore mbuf before return to pool

["Chen, Junjie J" <junjie.j.chen@intel.com>]

> >
> > dequeue zero copy change buf_addr and buf_iova of mbuf, and return to
> > mbuf pool without restore them, it breaks vm memory if others allocate
> > mbuf from same pool since mbuf reset doesn't reset buf_addr and
> buf_iova.
> >
> > Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>
> > ---
> >  lib/librte_vhost/virtio_net.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/lib/librte_vhost/virtio_net.c
> > b/lib/librte_vhost/virtio_net.c index 568ad0e..e9aaf6d 100644
> > --- a/lib/librte_vhost/virtio_net.c
> > +++ b/lib/librte_vhost/virtio_net.c
> > @@ -1158,6 +1158,26 @@ mbuf_is_consumed(struct rte_mbuf *m)
> >  	return true;
> >  }
> >
> > +
> > +static __rte_always_inline void
> > +restore_mbuf(struct rte_mbuf *m)
> > +{
> > +	uint32_t mbuf_size, priv_size;
> > +
> > +	while (m) {
> > +		priv_size = rte_pktmbuf_priv_size(m->pool);
> > +		mbuf_size = sizeof(struct rte_mbuf) + priv_size;
> > +		/* start of buffer is after mbuf structure and priv data */
> > +		m->priv_size = priv_size;
> 
> I don't think we need to restore priv_size. Refer to its definition in rte_mbuf:
>     "Size of the application private data. In case of an indirect mbuf, it
> stores the direct mbuf private data size."
> 
> Thanks,
> Jianfeng

You are right, I also remove restore for data_len since it is reset when allocating. Please see v2.
Thanks.

> 
> > +
> > +		m->buf_addr = (char *)m + mbuf_size;
> > +		m->buf_iova = rte_mempool_virt2iova(m) + mbuf_size;
> > +		m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM,
> > +			(uint16_t)m->buf_len);
> > +		m = m->next;
> > +	}
> > +}
> > +
> >  uint16_t
> >  rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
> >  	struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t
> > count)
> > @@ -1209,6 +1229,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t
> > queue_id,
> >  				nr_updated += 1;
> >
> >  				TAILQ_REMOVE(&vq->zmbuf_list, zmbuf, next);
> > +				restore_mbuf(zmbuf->mbuf);
> >  				rte_pktmbuf_free(zmbuf->mbuf);
> >  				put_zmbuf(zmbuf);
> >  				vq->nr_zmbuf -= 1;
> > --
> > 2.0.1