netdev - Re: [PATCH V2 3/6] vDPA: implement IRQ offloading helpers in vDPA core

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Date:   Mon, 20 Jul 2020 17:40:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Zhu, Lingshan" <lingshan.zhu@...el.com>, mst@...hat.com,
        alex.williamson@...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
Subject: Re: [PATCH V2 3/6] vDPA: implement IRQ offloading helpers in vDPA
 core


On 2020/7/20 下午5:07, Zhu, Lingshan wrote:
>>>
>>> +}
>>> +
>>> +static void vdpa_unsetup_irq(struct vdpa_device *vdev, int qid)
>>> +{
>>> +    struct vdpa_driver *drv = drv_to_vdpa(vdev->dev.driver);
>>> +
>>> +    if (drv->unsetup_vq_irq)
>>> +        drv->unsetup_vq_irq(vdev, qid);
>>
>>
>> Do you need to check the existence of drv before calling unset_vq_irq()?
> Yes, we should check this when we take the releasing path into account.
>>
>> And how can this synchronize with driver releasing and binding?
> Will add an vdpa_unsetup_irq() call in vhsot_vdpa_release().
> For binding, I think it is a new dev bound to the the driver,
> it should go through the vdpa_setup_irq() routine. or if it is
> a device re-bind to vhost_vdpa, I think we have cleaned up
> irq_bypass_producer for it as we would call vhdpa_unsetup_irq()
> in the release function.


I meant can the following things happen?

1) some vDPA device driver probe the hardware and call 
vdpa_request_irq() in its PCI probe function.
2) vDPA device is probed by vhost-vDPA

Then irq bypass can't work since we when vdpa_unsetup_irq() is called, 
there's no driver bound. Or is there a requirement that 
vdap_request/free_irq() must be called somewhere (e.g in the set_status 
bus operations)? If yes, we need document those requirements.

Thanks