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

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Message-ID: <CACGkMEsq+weeO7i8KtNNAPhXGwN=cTwWt3RWfTtML-Xwj3K5Qg@mail.gmail.com>
Date:   Tue, 20 Sep 2022 10:02:37 +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 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.

> ---
>  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.

>         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?

Thanks

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