netdev - Re: [PATCH 2/4] vDPA: only report driver features if FEATURES

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Date:   Wed, 21 Sep 2022 10:14:41 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Zhu, Lingshan" <lingshan.zhu@...el.com>
Cc:     mst <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>, kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/4] vDPA: only report driver features if FEATURES_OK is set

On Tue, Sep 20, 2022 at 1:46 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>
>
>
> On 9/20/2022 10:16 AM, Jason Wang wrote:
> > On Fri, Sep 9, 2022 at 5:05 PM Zhu Lingshan <lingshan.zhu@...el.com> wrote:
> >> vdpa_dev_net_config_fill() should only report driver features
> >> to userspace after features negotiation is done.
> >>
> >> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> >> ---
> >>   drivers/vdpa/vdpa.c | 13 +++++++++----
> >>   1 file changed, 9 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> >> index 798a02c7aa94..29d7e8858e6f 100644
> >> --- a/drivers/vdpa/vdpa.c
> >> +++ b/drivers/vdpa/vdpa.c
> >> @@ -819,6 +819,7 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
> >>          struct virtio_net_config config = {};
> >>          u64 features_device, features_driver;
> >>          u16 val_u16;
> >> +       u8 status;
> >>
> >>          vdev->config->get_config(vdev, 0, &config, sizeof(config));
> >>
> >> @@ -834,10 +835,14 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
> >>          if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
> >>                  return -EMSGSIZE;
> >>
> >> -       features_driver = vdev->config->get_driver_features(vdev);
> >> -       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
> >> -                             VDPA_ATTR_PAD))
> >> -               return -EMSGSIZE;
> >> +       /* only read driver features after the feature negotiation is done */
> >> +       status = vdev->config->get_status(vdev);
> >> +       if (status & VIRTIO_CONFIG_S_FEATURES_OK) {
> > Any reason this is not checked in its caller as what it used to do before?
> will check the existence of vdev->config->get_status before calling it in V2

Just to clarify, I meant to check FEAUTRES_OK in the caller -
vdpa_dev_config_fill() otherwise each type needs to repeat this in
their specific codes.

Thanks

>
> Thanks,
> Zhu Lingshan
> >
> > Thanks
> >
> >> +               features_driver = vdev->config->get_driver_features(vdev);
> >> +               if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
> >> +                                     VDPA_ATTR_PAD))
> >> +                       return -EMSGSIZE;
> >> +       }
> >>
> >>          features_device = vdev->config->get_device_features(vdev);
> >>
> >> --
> >> 2.31.1
> >>
>