vdpa: validate provisioned device features against specified attribute

With device feature provisioning, there's a chance for misconfiguration
that the vdpa feature attribute supplied in 'vdpa dev add' command doesn't
get selected on the device_features to be provisioned. For instance, when
a @mac attribute is specified, the corresponding feature bit _F_MAC in
device_features should be set for consistency. If there's conflict on
provisioned features against the attribute, it should be treated as an
error to fail the ambiguous command. Noted the opposite is not
necessarily true, for e.g. it's okay to have _F_MAC set in device_features
without providing a corresponding @mac attribute, in which case the vdpa
vendor driver could load certain default value for attribute that is not
explicitly specified.

Generalize this check in vdpa core so that there's no duplicate code in
each vendor driver.
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>
Message-Id: <1675725124-7375-4-git-send-email-si-wei.liu@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -606,8 +606,26 @@ 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]) {
+		u64 missing = 0x0ULL;
+
 		config.device_features =
 			nla_get_u64(nl_attrs[VDPA_ATTR_DEV_FEATURES]);
+		if (nl_attrs[VDPA_ATTR_DEV_NET_CFG_MACADDR] &&
+		    !(config.device_features & BIT_ULL(VIRTIO_NET_F_MAC)))
+			missing |= BIT_ULL(VIRTIO_NET_F_MAC);
+		if (nl_attrs[VDPA_ATTR_DEV_NET_CFG_MTU] &&
+		    !(config.device_features & BIT_ULL(VIRTIO_NET_F_MTU)))
+			missing |= BIT_ULL(VIRTIO_NET_F_MTU);
+		if (nl_attrs[VDPA_ATTR_DEV_NET_CFG_MAX_VQP] &&
+		    config.net.max_vq_pairs > 1 &&
+		    !(config.device_features & BIT_ULL(VIRTIO_NET_F_MQ)))
+			missing |= BIT_ULL(VIRTIO_NET_F_MQ);
+		if (missing) {
+			NL_SET_ERR_MSG_FMT_MOD(info->extack,
+					       "Missing features 0x%llx for provided attributes",
+					       missing);
+			return -EINVAL;
+		}
 		config.mask |= BIT_ULL(VDPA_ATTR_DEV_FEATURES);
 	}