Messages in this thread | | | Subject | Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf | From | Jason Wang <> | Date | Wed, 28 Apr 2021 21:08:35 +0800 |
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在 2021/4/28 下午6:20, Zhu, Lingshan 写道: > > > 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. >
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) >>>>>> >>>>> >>>> >>> >> >
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