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

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Message-ID: <4c711720-b4ff-6f09-61cb-2d305daa69c8@redhat.com>
Date:   Wed, 5 Aug 2020 16:06:50 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>, alex.williamson@...hat.com,
        mst@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, eli@...lanox.com, shahafs@...lanox.com,
        parav@...lanox.com
Subject: Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa


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;
> +	}
> +