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

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Date:   Wed, 21 Sep 2022 10:17:53 +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 1/4] vDPA: allow userspace to query features of a vDPA device

On Tue, Sep 20, 2022 at 5:58 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>
>
>
> On 9/20/2022 10:02 AM, Jason Wang wrote:
> > On Fri, Sep 9, 2022 at 5:05 PM Zhu Lingshan <lingshan.zhu@...el.com> 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@...el.com>
> > 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.

> >
> >>          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.

And

"/dev/vhost-vdpa0" is not a vDPA device but a vhost-vDPA device.

Thanks

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