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To: Stefan Hajnoczi <stefanha@redhat.com>, dev@dpdk.org
Cc: Yuanhan Liu <yliu@fridaylinux.org>, Tetsuya Mukawa <mtetsuyah@gmail.com>
References: <20171221164128.20001-1-stefanha@redhat.com>
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-ID: <95c9797f-3571-6843-0a79-7d3d1ed1a5c1@redhat.com>
Date: Thu, 21 Dec 2017 22:30:56 +0100
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Subject: Re: [dpdk-dev] [PATCH] vhost: introduce rte_vhost_vring_call()
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Hi Stefan,

On 12/21/2017 05:41 PM, Stefan Hajnoczi wrote:
> +int
> +rte_vhost_vring_call(int vid, uint16_t vring_idx)
> +{
> +	struct virtio_net *dev;
> +	struct vhost_virtqueue *vq;
> +
> +	dev = get_device(vid);
> +	if (!dev)
> +		return -1;
> +
> +	if (vring_idx >= VHOST_MAX_VRING)
> +		return -1;
> +
> +	vq = dev->virtqueue[vring_idx];
> +	if (!vq)
> +		return -1;
> +
> +	/* flush used->idx update before we read avail->flags. */
> +	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 0;
> +}

I think it may be better to have an internal function that just take the
vq as argument to avoid getting again the vq from the vid & vring index
in the hot path.

Also, this internal function could be tagged as always inlined.

Thanks,
Maxime