Re: [PATCH V3 6/6] vDPA/ifcvf: verify mandatory feature bits for vDPA

[Jason Wang <jasowang@xxxxxxxxxx>]

On 2021/3/11 12:16 下午, Zhu Lingshan wrote:
> On 3/11/2021 11:20 AM, Jason Wang wrote:
> > On 2021/3/10 5:00 下午, Zhu Lingshan wrote:
> > > vDPA requres VIRTIO_F_ACCESS_PLATFORM as a must, this commit
> > > examines this when set features.
> > >
> > > Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> > > ---
> > >   drivers/vdpa/ifcvf/ifcvf_base.c | 8 ++++++++
> > >   drivers/vdpa/ifcvf/ifcvf_base.h | 1 +
> > >   drivers/vdpa/ifcvf/ifcvf_main.c | 5 +++++
> > >   3 files changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c 
> > > b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > index ea6a78791c9b..58f47fdce385 100644
> > > --- a/drivers/vdpa/ifcvf/ifcvf_base.c
> > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > @@ -224,6 +224,14 @@ u64 ifcvf_get_features(struct ifcvf_hw *hw)
> > >       return hw->hw_features;
> > >   }
> > >   +int ifcvf_verify_min_features(struct ifcvf_hw *hw)
> > > +{
> > > +    if (!(hw->hw_features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
> > > +        return -EINVAL;
> > > +
> > > +    return 0;
> > > +}
> > > +
> > >   void ifcvf_read_net_config(struct ifcvf_hw *hw, u64 offset,
> > >                  void *dst, int length)
> > >   {
> > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
> > > b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > index dbb8c10aa3b1..91c5735d4dc9 100644
> > > --- a/drivers/vdpa/ifcvf/ifcvf_base.h
> > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
> > > @@ -123,6 +123,7 @@ void io_write64_twopart(u64 val, u32 *lo, u32 *hi);
> > >   void ifcvf_reset(struct ifcvf_hw *hw);
> > >   u64 ifcvf_get_features(struct ifcvf_hw *hw);
> > >   u64 ifcvf_get_hw_features(struct ifcvf_hw *hw);
> > > +int ifcvf_verify_min_features(struct ifcvf_hw *hw);
> > >   u16 ifcvf_get_vq_state(struct ifcvf_hw *hw, u16 qid);
> > >   int ifcvf_set_vq_state(struct ifcvf_hw *hw, u16 qid, u16 num);
> > >   struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw);
> > > diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
> > > b/drivers/vdpa/ifcvf/ifcvf_main.c
> > > index 25fb9dfe23f0..f624f202447d 100644
> > > --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> > > +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> > > @@ -179,6 +179,11 @@ static u64 ifcvf_vdpa_get_features(struct 
> > > vdpa_device *vdpa_dev)
> > >   static int ifcvf_vdpa_set_features(struct vdpa_device *vdpa_dev, 
> > > u64 features)
> > >   {
> > >       struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
> > > +    int ret;
> > > +
> > > +    ret = ifcvf_verify_min_features(vf);
> >
> >
> > So this validate device features instead of driver which is the one 
> > we really want to check?
> >
> > Thanks
>
> Hi Jason,
>
> Here we check device feature bits to make sure the device support 
> ACCESS_PLATFORM. 


If you want to check device features, you need to do that during probe() 
and fail the probing if without the feature. But I think you won't ship 
cards without ACCESS_PLATFORM.


> In get_features(),
> it will return a intersection of device features bit and driver 
> supported features bits(which includes ACCESS_PLATFORM).
> Other components like QEMU should not set features bits more than this 
> intersection of bits. so we can make sure if this
> ifcvf_verify_min_features() passed, both device and driver support 
> ACCESS_PLATFORM.
>
> Are you suggesting check driver feature bits in 
> ifcvf_verify_min_features() in the meantime as well?


So it really depends on your hardware. If you hardware can always offer 
ACCESS_PLATFORM, you just need to check driver features. This is how 
vdpa_sim and mlx5_vdpa work.

Thanks


> Thanks！
> > > +    if (ret)
> > > +        return ret;
> > >         vf->req_features = features;
> >
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