Re: [PATCH 1/4] vDPA: allow userspace to query features of a vDPA device

["Zhu, Lingshan" <lingshan.zhu@xxxxxxxxx>]

On 9/21/2022 10:17 AM, Jason Wang wrote:
> On Tue, Sep 20, 2022 at 5:58 PM Zhu, Lingshan <lingshan.zhu@xxxxxxxxx> wrote:
> > On 9/20/2022 10:02 AM, Jason Wang wrote:
> > > On Fri, Sep 9, 2022 at 5:05 PM Zhu Lingshan <lingshan.zhu@xxxxxxxxx> wrote:
> > > > This commit adds a new vDPA netlink attribution
> > > > VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES. Userspace can query
> > > > features of vDPA devices through this new attr.
> > > >
> > > > This commit invokes vdpa_config_ops.get_config() than
> > > > vdpa_get_config_unlocked() to read the device config
> > > > spcae, so no raeces in vdpa_set_features_unlocked()
> > > >
> > > > Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> > > It's better to share the userspace code as well.
> > OK, will share it in V2.
> > > > ---
> > > >    drivers/vdpa/vdpa.c       | 19 ++++++++++++++-----
> > > >    include/uapi/linux/vdpa.h |  4 ++++
> > > >    2 files changed, 18 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > > > index c06c02704461..798a02c7aa94 100644
> > > > --- a/drivers/vdpa/vdpa.c
> > > > +++ b/drivers/vdpa/vdpa.c
> > > > @@ -491,6 +491,8 @@ static int vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *m
> > > >                   err = -EMSGSIZE;
> > > >                   goto msg_err;
> > > >           }
> > > > +
> > > > +       /* report features of a vDPA management device through VDPA_ATTR_DEV_SUPPORTED_FEATURES */
> > > The code explains itself, there's no need for the comment.
> > these comments are required in other discussions
> I think it's more than sufficient to clarify the semantic where it is defined.
OK, then only comments in the header file
> > > >           if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_SUPPORTED_FEATURES,
> > > >                                 mdev->supported_features, VDPA_ATTR_PAD)) {
> > > >                   err = -EMSGSIZE;
> > > > @@ -815,10 +817,10 @@ static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
> > > >    static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
> > > >    {
> > > >           struct virtio_net_config config = {};
> > > > -       u64 features;
> > > > +       u64 features_device, features_driver;
> > > >           u16 val_u16;
> > > >
> > > > -       vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
> > > > +       vdev->config->get_config(vdev, 0, &config, sizeof(config));
> > > >
> > > >           if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
> > > >                       config.mac))
> > > > @@ -832,12 +834,19 @@ 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 = vdev->config->get_driver_features(vdev);
> > > > -       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features,
> > > > +       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);
> > > > +
> > > > +       /* report features of a vDPA device through VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES */
> > > > +       if (nla_put_u64_64bit(msg, VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES, features_device,
> > > >                                 VDPA_ATTR_PAD))
> > > >                   return -EMSGSIZE;
> > > >
> > > > -       return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
> > > > +       return vdpa_dev_net_mq_config_fill(vdev, msg, features_driver, &config);
> > > >    }
> > > >
> > > >    static int
> > > > diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> > > > index 25c55cab3d7c..97531b52dcbe 100644
> > > > --- a/include/uapi/linux/vdpa.h
> > > > +++ b/include/uapi/linux/vdpa.h
> > > > @@ -46,12 +46,16 @@ enum vdpa_attr {
> > > >
> > > >           VDPA_ATTR_DEV_NEGOTIATED_FEATURES,      /* u64 */
> > > >           VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,          /* u32 */
> > > > +       /* features of a vDPA management device */
> > > >           VDPA_ATTR_DEV_SUPPORTED_FEATURES,       /* u64 */
> > > >
> > > >           VDPA_ATTR_DEV_QUEUE_INDEX,              /* u32 */
> > > >           VDPA_ATTR_DEV_VENDOR_ATTR_NAME,         /* string */
> > > >           VDPA_ATTR_DEV_VENDOR_ATTR_VALUE,        /* u64 */
> > > >
> > > > +       /* features of a vDPA device, e.g., /dev/vhost-vdpa0 */
> > > > +       VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,  /* u64 */
> > > What's the difference between this and VDPA_ATTR_DEV_SUPPORTED_FEATURES?
> > This is to report a vDPA device features, and
> > VDPA_ATTR_DEV_SUPPORTED_FEATURES
> > is used for reporting the management device features, we have a long
> > discussion
> > on this before.
> Yes, but the comment is not clear in many ways:
>
> " features of a vDPA management device" sounds like features that is
> out of the scope of the virtio.
I think the term "vDPA device" implies that it is a virtio device.
So how about: "virtio features of a vDPA management device"
> And
>
> "/dev/vhost-vdpa0" is not a vDPA device but a vhost-vDPA device.
will remove this example here.

Thanks
> Thanks
>
> > > Thanks
> > >
> > > > +
> > > >           /* new attributes must be added above here */
> > > >           VDPA_ATTR_MAX,
> > > >    };
> > > > --
> > > > 2.31.1