[dpdk-dev] [PATCH v5 2/6] vhost: rewrite enqueue
Wang, Zhihong
zhihong.wang at intel.com
Wed Sep 14 10:22:39 CEST 2016
> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com]
> Sent: Tuesday, September 13, 2016 12:27 AM
> To: Wang, Zhihong <zhihong.wang at intel.com>; dev at dpdk.org
> Cc: yuanhan.liu at linux.intel.com; thomas.monjalon at 6wind.com
> Subject: Re: [PATCH v5 2/6] vhost: rewrite enqueue
>
>
>
> On 09/09/2016 05:39 AM, Zhihong Wang wrote:
> >
> > +static inline void __attribute__((always_inline))
> > +notify_guest(struct virtio_net *dev, struct vhost_virtqueue *vq)
> > +{
> > rte_smp_wmb();
> > -
> > - *(volatile uint16_t *)&vq->used->idx += count;
> > - vq->last_used_idx += count;
> > - vhost_log_used_vring(dev, vq,
> > - offsetof(struct vring_used, idx),
> > - sizeof(vq->used->idx));
> > -
> > - /* flush used->idx update before we read avail->flags. */
> Please don't remove comments if not justified.
> Here the comment is important, as it explains why the barrier is needed.
Okay.
> > + *(volatile uint16_t *)&vq->used->idx = vq->last_used_idx;
> > + vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
> > + sizeof(vq->used->idx));
> > rte_mb();
> > -
> > - /* Kick the guest if necessary. */
> > if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> > && (vq->callfd >= 0))
> > eventfd_write(vq->callfd, (eventfd_t)1);
> > - return count;
> > }
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