nvme: extend help message when mmap regs fails

Newer kernels enable the lockdown feature when secure boot is enabled.
This feature also prevents the register mapping into userspace. Thus it
is not enough to have CONFIG_IO_STRICT_DEVMEM disabled. Extend the
message with the hint also to disable secure boot.

While at it, also lower the reporting level to INFO, so that one single
'-v' is enough to get this information.

Signed-off-by: Daniel Wagner <dwagner@suse.de>

Author: igaw

nvme.c

@@ -5353,17 +5353,20 @@ static void *mmap_registers(struct nvme_dev *dev, bool writable)
 	sprintf(path, "/sys/class/nvme/%s/device/resource0", dev->name);
 	fd = open(path, writable ? O_RDWR : O_RDONLY);
 	if (fd < 0) {
-		if (log_level >= LOG_DEBUG)
+		if (log_level >= LOG_INFO)
 			nvme_show_error("%s did not find a pci resource, open failed %s",
 					dev->name, strerror(errno));
 		return NULL;
 	}
 
 	membase = mmap(NULL, getpagesize(), prot, MAP_SHARED, fd, 0);
 	if (membase == MAP_FAILED) {
-		if (log_level >= LOG_DEBUG) {
-			fprintf(stderr, "%s failed to map. ", dev->name);
-			fprintf(stderr, "Did your kernel enable CONFIG_IO_STRICT_DEVMEM?\n");
+		if (log_level >= LOG_INFO) {
+			fprintf(stderr, "Failed to map registers to userspace.\n\n"
+				"Did your kernel enable CONFIG_IO_STRICT_DEVMEM?\n"
+				"You can disable this feature with command line argument\n\n"
+				"\tio_memory=relaxed\n\n"
+				"Also ensure secure boot is disabled.\n\n");
 		}
 		membase = NULL;
 	}