Virtualization - Aug 2022 - [PATCH 1/2] vDPA: allow userspace to query features of a vDPA device

> From: Zhu, Lingshan <lingshan.zhu at intel.com>
> Sent: Monday, August 15, 2022 9:49 PM
> 
> On 8/16/2022 2:15 AM, Si-Wei Liu wrote:
> >
> >
> > On 8/15/2022 2:26 AM, Zhu Lingshan 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.
> >>
> >> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
> >> ---
> >> ? drivers/vdpa/vdpa.c?????? | 17 +++++++++++++----
> >> ? include/uapi/linux/vdpa.h |? 3 +++
> >> ? 2 files changed, 16 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index
> >> c06c02704461..efb55a06e961 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 */
> >> ????? if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_SUPPORTED_FEATURES,
> >> ??????????????????? mdev->supported_features, VDPA_ATTR_PAD)) {
> >> ????????? err = -EMSGSIZE;
> >> @@ -815,7 +817,7 @@ 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));
> >> @@ -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..d171b92ef522 100644
> >> --- a/include/uapi/linux/vdpa.h
> >> +++ b/include/uapi/linux/vdpa.h
> >> @@ -46,7 +46,10 @@ enum vdpa_attr {
> >> ? ????? VDPA_ATTR_DEV_NEGOTIATED_FEATURES,??? /* u64 */
> >> ????? VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,??????? /* u32 */
> >> +??? /* features of a vDPA management device */
Say comment as.
      /* Features of the vDPA management device matching the virtio feature bits
0 to 63 when queried on the mgmt. device.
        *  When returned on the vdpa device, it indicates virtio feature bits 0
to 63 of the vdpa device
        */
> >> ????? VDPA_ATTR_DEV_SUPPORTED_FEATURES,??? /* u64 */
> >> +??? /* features of a vDPA device, e.g., /dev/vhost-vdpa0 */
> >> +??? VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,??? /* u64 */
> > Append to the end, please. Otherwise it breaks userspace ABI.
> OK, will fix it in V2
I have read Se-Wei comment in the v4.
However I disagree, we don?t need to continue the past mistake done with the
naming.

Please add a comment that VDPA_ATTR_DEV_SUPPORTED_FEATURES like above about the
exception.
We established that there is no race condition either.
So no need to add new UAPI for some past history.