From: Zhu, Lingshan <redacted>
Sent: Tuesday, July 26, 2022 7:03 AM

On 7/24/2022 11:21 PM, Parav Pandit wrote:

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quoted

From: Zhu, Lingshan <redacted>
Sent: Saturday, July 23, 2022 7:24 AM


On 7/22/2022 9:12 PM, Parav Pandit wrote:

quoted

quoted

From: Zhu Lingshan <redacted>
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

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features

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of vDPA devices through this new attr.

Signed-off-by: Zhu Lingshan <redacted>
---
   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.

Please refer to our discussion in the V3 series, I have explained if re-use this
attr, it will be a multiple consumers and multiple produces model, it is a
typical racing condition.

I read the emails with subject = " Re: [PATCH V3 3/6] vDPA: allow userspace to query features of a vDPA device"
I couldn’t find multiple consumers multiple producers working on same nla message.