Messages in this thread | | | Subject | Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf | From | "Zhu, Lingshan" <> | Date | Wed, 28 Apr 2021 18:20:10 +0800 |
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On 4/28/2021 6:03 PM, Jason Wang wrote: > > 在 2021/4/28 下午5:56, Zhu, Lingshan 写道: >> >> >> On 4/28/2021 5:21 PM, Jason Wang wrote: >>> >>> 在 2021/4/28 下午4:59, Zhu, Lingshan 写道: >>>> >>>> >>>> On 4/28/2021 4:42 PM, Jason Wang wrote: >>>>> >>>>> 在 2021/4/28 下午4:21, 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@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. >> when calling this, I think it targets a usersapce program, why kernel >> space need it, so IMHO no harm if we check this to keep the parent >> driver robust. > > > Again, vDPA device is unaware of what driver that is bound. It could > be virtio-vpda, vhost-vdpa or other in the future. It's only the vDPA > bus driver know how it is actually used. > > >>> >>> >>>>> 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. >> If it is not page aligned, there would be extra complexities for >> vhost/qemu, I see it as a hardware defect, > > > It is allowed by the virtio spec, isn't it? The spec does not require the doorbell to be page size aligned, however it still a hardware defect if non page size aligned notify base present, I will leave a warning message here instead of the 0 value.
Thanks Zhu Lingshan > > Thanks > > >> why adapt to this kind of defects? >> >> Thanks >> Zhu Lingshan >>> >>> 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) >>>>> >>>> >>> >> >
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