1 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 1b37b28cc234..d0ac72cc19ff 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -231,6 +231,32 @@ Dump-capture kernel config options (Arch Dependent, ia64)
   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
 =======================