[PATCH 1 of 2] kdump pv-on-hvm: introduce "reset_devices" command line option

[Olaf Hering <olaf@aepfle.de>]

# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1301997980 -7200
# Node ID 6cc1c07f0e74cd481d1cde0f17bec2631a767891
# Parent  0bee20f8e418d32ab5828eb57c7542ca27ce425d
kdump pv-on-hvm: introduce "reset_devices" command line option

    upstream commit 7e96287ddc4f42081e18248b6167041c0908004c

    [PATCH] kdump: introduce "reset_devices" command line option

    Resetting the devices during driver initialization can be a costly
    operation in terms of time (especially scsi devices).  This option can be
    used by drivers to know that user forcibly wants the devices to be reset
    during initialization.

    This option can be useful while kernel is booting in unreliable
    environment.  For ex.  during kdump boot where devices are in unknown
    random state and BIOS execution has been skipped.

    Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

---
 Documentation/kernel-parameters.txt |    3 +++
 include/linux/init.h                |    1 +
 init/main.c                         |   20 ++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff -r 0bee20f8e418 -r 6cc1c07f0e74 Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt	Sat Apr 02 15:54:29 2011 +0100
+++ b/Documentation/kernel-parameters.txt	Tue Apr 05 12:06:20 2011 +0200
@@ -1392,6 +1392,9 @@
 
 	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
 
+	reset_devices	[KNL] Force drivers to reset the underlying device
+			during initialization.
+
 	resume=		[SWSUSP]
 			Specify the partition device for software suspend
 
diff -r 0bee20f8e418 -r 6cc1c07f0e74 include/linux/init.h
--- a/include/linux/init.h	Sat Apr 02 15:54:29 2011 +0100
+++ b/include/linux/init.h	Tue Apr 05 12:06:20 2011 +0200
@@ -68,6 +68,7 @@
 
 /* Defined in init/main.c */
 extern char saved_command_line[];
+extern unsigned int reset_devices;
 
 /* used by init/main.c */
 extern void setup_arch(char **);
diff -r 0bee20f8e418 -r 6cc1c07f0e74 init/main.c
--- a/init/main.c	Sat Apr 02 15:54:29 2011 +0100
+++ b/init/main.c	Tue Apr 05 12:06:20 2011 +0200
@@ -128,6 +128,18 @@
 static unsigned int max_cpus = NR_CPUS;
 
 /*
+ * If set, this is an indication to the drivers that reset the underlying
+ * device before going ahead with the initialization otherwise driver might
+ * rely on the BIOS and skip the reset operation.
+ *
+ * This is useful if kernel is booting in an unreliable environment.
+ * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
+ * skipped and devices will be in unknown state.
+ */
+unsigned int reset_devices;
+EXPORT_SYMBOL(reset_devices);
+
+/*
  * Setup routine for controlling SMP activation
  *
  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
@@ -153,6 +165,14 @@
 
 __setup("maxcpus=", maxcpus);
 
+static int __init set_reset_devices(char *str)
+{
+	reset_devices = 1;
+	return 1;
+}
+
+__setup("reset_devices", set_reset_devices);
+
 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
 static const char *panic_later, *panic_param;