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

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

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