Re: [PATCH 1/3] vDPA/ifcvf: deduce VIRTIO device ID when probe

[Zhu Lingshan <lingshan.zhu@xxxxxxxxxxxxxxx>]

On 4/15/2021 3:16 PM, Jason Wang wrote:
> 在 2021/4/15 下午2:36, Zhu Lingshan 写道:
> > On 4/15/2021 2:30 PM, Jason Wang wrote:
> > > 在 2021/4/15 下午1:52, Zhu Lingshan 写道:
> > > > On 4/15/2021 11:30 AM, Jason Wang wrote:
> > > > > 在 2021/4/14 下午5:18, Zhu Lingshan 写道:
> > > > > > This commit deduces VIRTIO device ID as device type when probe,
> > > > > > then ifcvf_vdpa_get_device_id() can simply return the ID.
> > > > > > ifcvf_vdpa_get_features() and ifcvf_vdpa_get_config_size()
> > > > > > can work properly based on the device ID.
> > > > > >
> > > > > > Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> > > > > > ---
> > > > > >   drivers/vdpa/ifcvf/ifcvf_base.h |  1 +
> > > > > >   drivers/vdpa/ifcvf/ifcvf_main.c | 22 ++++++++++------------
> > > > > >   2 files changed, 11 insertions(+), 12 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
> > > > > > b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > > > > index b2eeb16b9c2c..1c04cd256fa7 100644
> > > > > > --- a/drivers/vdpa/ifcvf/ifcvf_base.h
> > > > > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > > > > @@ -84,6 +84,7 @@ struct ifcvf_hw {
> > > > > >       u32 notify_off_multiplier;
> > > > > >       u64 req_features;
> > > > > >       u64 hw_features;
> > > > > > +    u32 dev_type;
> > > > > >       struct virtio_pci_common_cfg __iomem *common_cfg;
> > > > > >       void __iomem *net_cfg;
> > > > > >       struct vring_info vring[IFCVF_MAX_QUEUE_PAIRS * 2];
> > > > > > diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
> > > > > > b/drivers/vdpa/ifcvf/ifcvf_main.c
> > > > > > index 44d7586019da..99b0a6b4c227 100644
> > > > > > --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> > > > > > +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> > > > > > @@ -323,19 +323,9 @@ static u32 ifcvf_vdpa_get_generation(struct 
> > > > > > vdpa_device *vdpa_dev)
> > > > > >     static u32 ifcvf_vdpa_get_device_id(struct vdpa_device 
> > > > > > *vdpa_dev)
> > > > > >   {
> > > > > > -    struct ifcvf_adapter *adapter = vdpa_to_adapter(vdpa_dev);
> > > > > > -    struct pci_dev *pdev = adapter->pdev;
> > > > > > -    u32 ret = -ENODEV;
> > > > > > -
> > > > > > -    if (pdev->device < 0x1000 || pdev->device > 0x107f)
> > > > > > -        return ret;
> > > > > > -
> > > > > > -    if (pdev->device < 0x1040)
> > > > > > -        ret =  pdev->subsystem_device;
> > > > > > -    else
> > > > > > -        ret =  pdev->device-0x1040;
> > > > > > +    struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
> > > > > >   -    return ret;
> > > > > > +    return vf->dev_type;
> > > > > >   }
> > > > > >     static u32 ifcvf_vdpa_get_vendor_id(struct vdpa_device 
> > > > > > *vdpa_dev)
> > > > > > @@ -466,6 +456,14 @@ static int ifcvf_probe(struct pci_dev *pdev, 
> > > > > > const struct pci_device_id *id)
> > > > > >       pci_set_drvdata(pdev, adapter);
> > > > > >         vf = &adapter->vf;
> > > > > > +    if (pdev->device < 0x1000 || pdev->device > 0x107f)
> > > > > > +        return -EOPNOTSUPP;
> > > > > > +
> > > > > > +    if (pdev->device < 0x1040)
> > > > > > +        vf->dev_type =  pdev->subsystem_device;
> > > > > > +    else
> > > > > > +        vf->dev_type =  pdev->device - 0x1040;
> > > > >
> > > > >
> > > > > So a question here, is the device a transtional device or modern one?
> > > > >
> > > > > If it's a transitonal one, can it swtich endianess automatically 
> > > > > or not?
> > > > >
> > > > > Thanks
> > > > Hi Jason,
> > > >
> > > > This driver should drive both modern and transitional devices as we 
> > > > discussed before.
> > > > If it's a transitional one, it will act as a modern device by 
> > > > default, legacy mode is a fail-over path.
> > >
> > >
> > > Note that legacy driver use native endian, support legacy driver 
> > > requires the device to know native endian which I'm not sure your 
> > > device can do that.
> > >
> > > Thanks
> > Yes, legacy requires guest native endianess, I think we don't need to 
> > worry about this because our transitional device should work in 
> > modern mode by
> > default(legacy mode is the failover path we will never reach, 
> > get_features will fail if no ACCESS_PLATFORM), we don't support 
> > legacy device in vDPA.
> >
> > Thanks
>
>
> Ok, so I think it's better to add a comment here.
sure, will add a comment in V2

Thanks
> Thanks
>
>
> > > > For vDPA, it has to support VIRTIO_1 and ACCESS_PLATFORM, so it 
> > > > must in modern mode.
> > > > I think we don't need to worry about endianess for legacy mode.
> > > >
> > > > Thanks
> > > > Zhu Lingshan
> > > > > > +
> > > > > >       vf->base = pcim_iomap_table(pdev);
> > > > > >         adapter->pdev = pdev;