Messages in this thread | | | Subject | Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf | From | "Zhu, Lingshan" <> | Date | Thu, 29 Apr 2021 19:26:14 +0800 |
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On 4/28/2021 9:08 PM, Jason Wang wrote: > > 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). For the page alignment checks, I think this is the point of using PAGE_SIZE, we want the doorbell placed at the page boundary, PAGE_SIZE depends on the arch, so I think we don't want to use hard code here. We will pass the notify_pa to upper layer anyway, just print an warning if not PAGE_SIZE aligned.
However I think this may refer to vdpa_notification_area.size, YES, I think use PAGE_SIZE directly is wrong here, this size depends on the device(bar layout) than the arch, so I will add more code to tell which device is probed by the driver, then assign correct value.
Thanks > > 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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