Add documentation for extended crashkernel syntax

This adds the documentation for the extended crashkernel syntax into Documentation/kdump/kdump.txt. Signed-off-by: Bernhard Walle <bwalle@suse.de> Cc: Andi Kleen <ak@suse.de> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Vivek Goyal <vgoyal@in.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add documentation for extended crashkernel syntax
This adds the documentation for the extended crashkernel syntax into Documentation/kdump/kdump.txt. Signed-off-by: Bernhard Walle <bwalle@suse.de> Cc: Andi Kleen <ak@suse.de> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Vivek Goyal <vgoyal@in.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Bernhard Walle · Linus Torvalds
1 parent 7d7712a385
Showing 2 changed files with 33 additions and 0 deletions Side-by-side Diff
Documentation/kdump/kdump.txt
Documentation/kernel-parameters.txt
@@ -231,6 +231,32 @@
   any space below the alignment point will be wasted.
  
  
+Extended crashkernel syntax
+===========================
+
+While the "crashkernel=size[@offset]" syntax is sufficient for most
+configurations, sometimes it's handy to have the reserved memory dependent
+on the value of System RAM -- that's mostly for distributors that pre-setup
+the kernel command line to avoid a unbootable system after some memory has
+been removed from the machine.
+
+The syntax is:
+
+    crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+    range=start-[end]
+
+For example:
+
+    crashkernel=512M-2G:64M,2G-:128M
+
+This would mean:
+
+    1) if the RAM is smaller than 512M, then don't reserve anything
+       (this is the "rescue" case)
+    2) if the RAM size is between 512M and 2G, then reserve 64M
+    3) if the RAM size is larger than 2G, then reserve 128M
+
+
 Boot into System Kernel
 =======================
  
@@ -497,6 +497,13 @@
 			[KNL] Reserve a chunk of physical memory to
 			hold a kernel to switch to with kexec on panic.
  
+	crashkernel=range1:size1[,range2:size2,...][@offset]
+			[KNL] Same as above, but depends on the memory
+			in the running system. The syntax of range is
+			start-[end] where start and end are both
+			a memory unit (amount[KMG]). See also
+			Documentation/kdump/kdump.txt for a example.
+
 	cs4232=		[HW,OSS]
 			Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
...	...	@@ -231,6 +231,32 @@
231	231	any space below the alignment point will be wasted.
232	232
233	233
	234	+Extended crashkernel syntax
	235	+===========================
	236	+
	237	+While the "crashkernel=size[@offset]" syntax is sufficient for most
	238	+configurations, sometimes it's handy to have the reserved memory dependent
	239	+on the value of System RAM -- that's mostly for distributors that pre-setup
	240	+the kernel command line to avoid a unbootable system after some memory has
	241	+been removed from the machine.
	242	+
	243	+The syntax is:
	244	+
	245	+ crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
	246	+ range=start-[end]
	247	+
	248	+For example:
	249	+
	250	+ crashkernel=512M-2G:64M,2G-:128M
	251	+
	252	+This would mean:
	253	+
	254	+ 1) if the RAM is smaller than 512M, then don't reserve anything
	255	+ (this is the "rescue" case)
	256	+ 2) if the RAM size is between 512M and 2G, then reserve 64M
	257	+ 3) if the RAM size is larger than 2G, then reserve 128M
	258	+
	259	+
234	260	Boot into System Kernel
235	261	=======================
236	262
...	...	@@ -497,6 +497,13 @@
497	497	[KNL] Reserve a chunk of physical memory to
498	498	hold a kernel to switch to with kexec on panic.
499	499
	500	+ crashkernel=range1:size1[,range2:size2,...][@offset]
	501	+ [KNL] Same as above, but depends on the memory
	502	+ in the running system. The syntax of range is
	503	+ start-[end] where start and end are both
	504	+ a memory unit (amount[KMG]). See also
	505	+ Documentation/kdump/kdump.txt for a example.
	506	+
500	507	cs4232= [HW,OSS]
501	508	Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
502	509