Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

From: Jason Wang <jasowang@redhat.com>
To: Zhu Lingshan <lingshan.zhu@intel.com>,
	alex.williamson@redhat.com, mst@redhat.com, pbonzini@redhat.com,
	sean.j.christopherson@intel.com, wanpengli@tencent.com
Cc: shahafs@mellanox.com, parav@mellanox.com, kvm@vger.kernel.org,
	netdev@vger.kernel.org,
	virtualization@lists.linux-foundation.org, eli@mellanox.com
Subject: Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa
Date: Wed, 5 Aug 2020 16:06:50 +0800	[thread overview]
Message-ID: <4c711720-b4ff-6f09-61cb-2d305daa69c8@redhat.com> (raw)
In-Reply-To: <20200731065533.4144-5-lingshan.zhu@intel.com>

On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
> +{
> +	struct vhost_virtqueue *vq = &v->vqs[qid];
> +	const struct vdpa_config_ops *ops = v->vdpa->config;
> +	struct vdpa_device *vdpa = v->vdpa;
> +	int ret, irq;
> +
> +	spin_lock(&vq->call_ctx.ctx_lock);
> +	irq = ops->get_vq_irq(vdpa, qid);

Btw, this assumes that get_vq_irq is mandatory. This looks wrong since 
there's no guarantee that the vDPA device driver can see irq. And this 
break vdpa simulator.

Let's add a check and make it optional by document this assumption in 
the vdpa.h.

Thanks

> +	if (!vq->call_ctx.ctx || irq < 0) {
> +		spin_unlock(&vq->call_ctx.ctx_lock);
> +		return;
> +	}
> +

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