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

[ Upstream commit 14a1336e6fff47dd1028b484d6c802105c58e2ee ]

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

drivers/nvme/host/nvme.h

@@ -537,6 +537,9 @@ 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)