nvme: warn when finding multi-port subsystems without multipathing enabled

Without CONFIG_NVME_MULTIPATH enabled a multi-port subsystem might
show up as invididual devices and cause problems, warn about it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/nvme.h

@@ -531,6 +531,9 @@ static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
 static inline int nvme_mpath_init(struct nvme_ctrl *ctrl,
 		struct nvme_id_ctrl *id)
 {
+	if (ctrl->subsys->cmic & (1 << 3))
+		dev_warn(ctrl->device,
+"Please enable CONFIG_NVME_MULTIPATH for full support of multi-port devices.\n");
 	return 0;
 }
 static inline void nvme_mpath_uninit(struct nvme_ctrl *ctrl)