NVMe: Add nvme subsystem reset IOCTL

Controllers can perform optional subsystem resets as introduced in NVMe
1.1. This patch adds an IOCTL to trigger the subsystem reset by writing
"NVMe" to the NSSR register.

Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index d6b5600..b5812c3 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -28,7 +28,7 @@
 	__u32			cc;	/* Controller Configuration */
 	__u32			rsvd1;	/* Reserved */
 	__u32			csts;	/* Controller Status */
-	__u32			rsvd2;	/* Reserved */
+	__u32			nssr;	/* Subsystem Reset */
 	__u32			aqa;	/* Admin Queue Attributes */
 	__u64			asq;	/* Admin SQ Base Address */
 	__u64			acq;	/* Admin CQ Base Address */
diff --git a/include/uapi/linux/nvme.h b/include/uapi/linux/nvme.h
index 732b32e..8864194 100644
--- a/include/uapi/linux/nvme.h
+++ b/include/uapi/linux/nvme.h
@@ -584,5 +584,6 @@
 #define NVME_IOCTL_SUBMIT_IO	_IOW('N', 0x42, struct nvme_user_io)
 #define NVME_IOCTL_IO_CMD	_IOWR('N', 0x43, struct nvme_passthru_cmd)
 #define NVME_IOCTL_RESET	_IO('N', 0x44)
+#define NVME_IOCTL_SUBSYS_RESET	_IO('N', 0x45)
 
 #endif /* _UAPI_LINUX_NVME_H */