Jason Wang
2021-Apr-28 13:08 UTC
[PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf
? 2021/4/28 ??6:20, Zhu, Lingshan ??:> > > On 4/28/2021 6:03 PM, Jason Wang wrote: >> >> ? 2021/4/28 ??5:56, Zhu, Lingshan ??: >>> >>> >>> On 4/28/2021 5:21 PM, Jason Wang wrote: >>>> >>>> ? 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. >>> 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. >Another note is that, using PAGE_SIZE is wrong here since it varies among archs (at most 64K on some one). Thanks> 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) >>>>>> >>>>> >>>> >>> >> >