Virtualization - Apr 2021 - [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf

? 2021/4/28 ??4:59, Zhu, Lingshan ??:
>
>
> On 4/28/2021 4:42 PM, Jason Wang wrote:
>>
>> ? 2021/4/28 ??4:21, Zhu Lingshan ??:
>>> 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 at intel.com>
>>> ---
>>> ? drivers/vdpa/ifcvf/ifcvf_main.c | 18 ++++++++++++++++++
>>> ? 1 file changed, 18 insertions(+)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index e48e6b74fe2e..afcb71bc0f51 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -413,6 +413,23 @@ 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_hw *vf = vdpa_to_vf(vdpa_dev);
>>> +??? struct vdpa_notification_area area;
>>> +
>>> +??? if (vf->notify_pa % PAGE_SIZE) {
>>> +??????? area.addr = 0;
>>> +??????? area.size = 0;
>>
>>
>> We don't need this since:
>>
>> 1) there's a check in the vhost vDPA
> I think you mean this code block in vdpa.c
> ??????? notify = ops->get_vq_notification(vdpa, index);
> ??????? if (notify.addr & (PAGE_SIZE - 1))
> ??????????????? return -EINVAL;
>
> This should work, however, I think the parent driver should ensure it 
> passes a PAGE_SIZE aligned address to userspace, to be robust, to be 
> reliable.

The point is parent is unaware of whether or not there's a userspace.

>> 2) device is unaware of the bound driver, non page aligned doorbell 
>> doesn't necessarily meant it can be used
> Yes, non page aligned doorbell can not be used, so there is a check.

Typo, what I meant is "it can't be used". That is to say, we
should let
the vDPA bus driver to decide whether or not it can be used.

Thanks

>
> Thanks
> Zhu Lingshan
>>
>> Let's leave those polices to the driver.
>>
>> Thanks
>>
>>
>>> +??? } else {
>>> +??????? area.addr = vf->notify_pa;
>>> +??????? area.size = PAGE_SIZE;
>>> +??? }
>>> +
>>> +??? return area;
>>> +}
>>> +
>>> ? /*
>>> ?? * IFCVF currently does't have on-chip IOMMU, so not
>>> ?? * implemented set_map()/dma_map()/dma_unmap()
>>> @@ -440,6 +457,7 @@ 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)
>>
>