netdev - Re: [PATCH V3 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf

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Date:   Tue, 1 Jun 2021 16:57:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Zhu, Lingshan" <lingshan.zhu@...el.com>, mst@...hat.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH V3 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf


在 2021/6/1 下午4:56, Zhu, Lingshan 写道:
>
>
> On 6/1/2021 4:50 PM, Jason Wang wrote:
>>
>> 在 2021/6/1 下午2:28, Zhu Lingshan 写道:
>>> This commit implements doorbell mapping feature for ifcvf.
>>> This feature maps the notify page to userspace, to eliminate
>>> vmexit when kick a vq.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>> ---
>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 21 +++++++++++++++++++++
>>>   1 file changed, 21 insertions(+)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index ab0ab5cf0f6e..d41db042612c 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -413,6 +413,26 @@ static int ifcvf_vdpa_get_vq_irq(struct 
>>> vdpa_device *vdpa_dev,
>>>       return vf->vring[qid].irq;
>>>   }
>>>   +static struct vdpa_notification_area 
>>> ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev,
>>> +                                   u16 idx)
>>> +{
>>> +    struct ifcvf_adapter *adapter = vdpa_to_adapter(vdpa_dev);
>>> +    struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>>> +    struct pci_dev *pdev = adapter->pdev;
>>> +    struct vdpa_notification_area area;
>>> +
>>> +    area.addr = vf->vring[idx].notify_pa;
>>> +    if (!vf->notify_off_multiplier)
>>> +        area.size = PAGE_SIZE;
>>> +    else
>>> +        area.size = vf->notify_off_multiplier;
>>> +
>>> +    if (area.addr % PAGE_SIZE)
>>> +        IFCVF_DBG(pdev, "vq %u doorbell address is not PAGE_SIZE 
>>> aligned\n", idx);
>>
>>
>> I don't see the reason to keep this, or get_notification is not the 
>> proper place to do this kind of warning.
>>
>> Thanks
> some customers have ever complained have troubles to enable such 
> features with their IP,
> I think this can help them debug.


If you want to do this, the ifcvf_init_hw() is the proper place.

Note that this function is called by userspace.

Thanks


>
> Thanks
>>
>>
>>> +
>>> +    return area;
>>> +}
>>> +
>>>   /*
>>>    * IFCVF currently does't have on-chip IOMMU, so not
>>>    * implemented set_map()/dma_map()/dma_unmap()
>>> @@ -440,6 +460,7 @@ static const struct vdpa_config_ops ifc_vdpa_ops 
>>> = {
>>>       .get_config    = ifcvf_vdpa_get_config,
>>>       .set_config    = ifcvf_vdpa_set_config,
>>>       .set_config_cb  = ifcvf_vdpa_set_config_cb,
>>> +    .get_vq_notification = ifcvf_get_vq_notification,
>>>   };
>>>     static int ifcvf_probe(struct pci_dev *pdev, const struct 
>>> pci_device_id *id)
>>
>