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

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Message-ID: <CACGkMEuXA6Uj7OHqUDux=Yz+XFtouKWGOVV4fk5B5XCZW5F22w@mail.gmail.com>
Date:   Wed, 21 Sep 2022 15:43:49 +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 Wed, Sep 21, 2022 at 1:39 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>
>
>
> On 9/21/2022 10:14 AM, Jason Wang wrote:
> > 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.
> if we check FEATURES_OK in the caller vdpa_dev_config_fill(), then
> !FEATURES_OK will block reporting all attributions, for example
> the device features and virtio device config space fields in this series
> and device status.
> Currently only driver features needs to check FEATURES_OK.
> Or did I missed anything?

I don't see much difference, we just move the following part to the
caller, it is not the config but the VDPA_ATTR_DEV_NEGOTIATED_FEATURES
is blocked.

Thanks

>
> Thanks
> >
> > 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
> >>>>
>