vdpa: device feature provisioning

This patch allows the device features to be provisioned through
netlink. A new attribute is introduced to allow the userspace to pass
a 64bit device features during device adding.

This provides several advantages:

- Allow to provision a subset of the features to ease the cross vendor
  live migration.
- Better debug-ability for vDPA framework and parent.

Reviewed-by: Eli Cohen <elic@nvidia.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220927074810.28627-2-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -600,6 +600,11 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
 		}
 		config.mask |= BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP);
 	}
+	if (nl_attrs[VDPA_ATTR_DEV_FEATURES]) {
+		config.device_features =
+			nla_get_u64(nl_attrs[VDPA_ATTR_DEV_FEATURES]);
+		config.mask |= BIT_ULL(VDPA_ATTR_DEV_FEATURES);
+	}
 
 	/* Skip checking capability if user didn't prefer to configure any
 	 * device networking attributes. It is likely that user might have used

include/linux/vdpa.h

@@ -104,6 +104,7 @@ struct vdpa_iova_range {
 };
 
 struct vdpa_dev_set_config {
+	u64 device_features;
 	struct {
 		u8 mac[ETH_ALEN];
 		u16 mtu;

include/uapi/linux/vdpa.h

@@ -52,6 +52,8 @@ enum vdpa_attr {
 	VDPA_ATTR_DEV_VENDOR_ATTR_NAME,		/* string */
 	VDPA_ATTR_DEV_VENDOR_ATTR_VALUE,        /* u64 */
 
+	VDPA_ATTR_DEV_FEATURES,                 /* u64 */
+
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,
 };