netdev - RE: [PATCH V4 3/6] vDPA: allow userspace to query features of a vDPA device

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Date:   Sun, 24 Jul 2022 15:21:32 +0000
From:   Parav Pandit <parav@...dia.com>
To:     "Zhu, Lingshan" <lingshan.zhu@...el.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "mst@...hat.com" <mst@...hat.com>
CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xieyongji@...edance.com" <xieyongji@...edance.com>,
        "gautam.dawar@....com" <gautam.dawar@....com>
Subject: RE: [PATCH V4 3/6] vDPA: allow userspace to query features of a vDPA
 device



> From: Zhu, Lingshan <lingshan.zhu@...el.com>
> Sent: Saturday, July 23, 2022 7:24 AM
> 
> 
> On 7/22/2022 9:12 PM, Parav Pandit wrote:
> >> From: Zhu Lingshan <lingshan.zhu@...el.com>
> >> Sent: Friday, July 22, 2022 7:53 AM
> >>
> >> 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@...el.com>
> >> ---
> >>   drivers/vdpa/vdpa.c       | 13 +++++++++----
> >>   include/uapi/linux/vdpa.h |  1 +
> >>   2 files changed, 10 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index
> >> ebf2f363fbe7..9b0e39b2f022 100644
> >> --- a/drivers/vdpa/vdpa.c
> >> +++ b/drivers/vdpa/vdpa.c
> >> @@ -815,7 +815,7 @@ 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 +832,17 @@ 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);
> >> +	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..39f1c3d7c112 100644
> >> --- a/include/uapi/linux/vdpa.h
> >> +++ b/include/uapi/linux/vdpa.h
> >> @@ -47,6 +47,7 @@ enum vdpa_attr {
> >>   	VDPA_ATTR_DEV_NEGOTIATED_FEATURES,	/* u64 */
> >>   	VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,		/* u32 */
> >>   	VDPA_ATTR_DEV_SUPPORTED_FEATURES,	/* u64 */
> >> +	VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,	/* u64 */
> >>
> > I have answered in previous emails.
> > I disagree with the change.
> > Please reuse VDPA_ATTR_DEV_SUPPORTED_FEATURES.
> I believe we have already discussed this before in the V3 thread.
> I have told you that reusing this attr will lead to a new race condition.
>
Returning attribute cannot lead to any race condition.

 
> Pleas refer to the previous thread, and you did not answer my questions in
> that thread.
> 
> Thanks,
> Zhu Lingshan
> >
> > MST,
> > I nack this patch.
> > As mentioned in the previous versions, also it is missing the example
> output in the commit log.
> > Please include example output.
> >
> >>   	VDPA_ATTR_DEV_QUEUE_INDEX,              /* u32 */
> >>   	VDPA_ATTR_DEV_VENDOR_ATTR_NAME,		/* string */
> >> --
> >> 2.31.1