Re: [PATCH 1/2] vDPA/ifcvf: record virtio notify base

[Jason Wang <jasowang@xxxxxxxxxx>]

在 2021/4/28 下午6:00, Zhu, Lingshan 写道:
> On 4/28/2021 4:39 PM, Jason Wang wrote:
> > 在 2021/4/28 下午4:21, Zhu Lingshan 写道:
> > > This commit records virtio notify base addr to implemente
> > > doorbell mapping feature
> > >
> > > Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> > > ---
> > >   drivers/vdpa/ifcvf/ifcvf_base.c | 1 +
> > >   drivers/vdpa/ifcvf/ifcvf_base.h | 1 +
> > >   2 files changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c 
> > > b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > index 1a661ab45af5..cc61a5bfc5b1 100644
> > > --- a/drivers/vdpa/ifcvf/ifcvf_base.c
> > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > @@ -133,6 +133,7 @@ int ifcvf_init_hw(struct ifcvf_hw *hw, struct 
> > > pci_dev *pdev)
> > > &hw->notify_off_multiplier);
> > >               hw->notify_bar = cap.bar;
> > >               hw->notify_base = get_cap_addr(hw, &cap);
> > > +            hw->notify_pa = pci_resource_start(pdev, cap.bar) + 
> > > cap.offset;
> >
> >
> > To be more generic and avoid future changes, let's use the math 
> > defined in the virtio spec.
> >
> > You may refer how it is implemented in virtio_pci vdpa driver[1].
> Are you suggesting every vq keep its own notify_pa? In this case, we 
> still need to record notify_pa in hw when init_hw, then initialize 
> vq->notify_pa accrediting to hw->notify_pa.


I meant you need to follow how virtio spec did to calculate the doorbell 
address per vq:

        cap.offset + queue_notify_off * notify_off_multiplier

Obviously, you ignore queue_notify_off and notify_off_multiplier here. 
This may bring troubles for the existing device IFCVF and future devices.

If I understand correctly, this device can be probed by virtio-pci 
driver which use the above math. There's no reason for using ad-hoc hack.

Thanks


> Thanks
> Zhu Lingshan
> > Thanks
> >
> > [1] 
> > https://lore.kernel.org/virtualization/20210415073147.19331-5-jasowang@xxxxxxxxxx/T/
> >
> >
> > > IFCVF_DBG(pdev, "hw->notify_base = %p\n",
> > >                     hw->notify_base);
> > >               break;
> > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
> > > b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > index 0111bfdeb342..bcca7c1669dd 100644
> > > --- a/drivers/vdpa/ifcvf/ifcvf_base.h
> > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > @@ -98,6 +98,7 @@ struct ifcvf_hw {
> > >       char config_msix_name[256];
> > >       struct vdpa_callback config_cb;
> > >       unsigned int config_irq;
> > > +    phys_addr_t  notify_pa;
> > >   };
> > >     struct ifcvf_adapter {

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