1 files changed, 41 insertions, 8 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index b3dbf11eb82c..715632026073 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -565,23 +565,56 @@ config CRASH_DUMP
           PHYSICAL_START.
           For more details see Documentation/kdump/kdump.txt
 
+config RELOCATABLE
+        bool "Build a relocatable kernel(EXPERIMENTAL)"
+        depends on EXPERIMENTAL
+        help
+          Builds a relocatable kernel. This enables loading and running
+          a kernel binary from a different physical address than it has
+          been compiled for.
+
+          One use is for the kexec on panic case where the recovery kernel
+          must live at a different physical address than the primary
+          kernel.
+
+          Note: If CONFIG_RELOCATABLE=y, then kernel run from the address
+          it has been loaded at and compile time physical address
+          (CONFIG_PHYSICAL_START) is ignored.
+
 config PHYSICAL_START
         hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)
-        default "0x1000000" if CRASH_DUMP
         default "0x200000"
         help
-          This gives the physical address where the kernel is loaded. Normally
-          for regular kernels this value is 0x200000 (2MB). But in the case
-          of kexec on panic the fail safe kernel needs to run at a different
-          address than the panic-ed kernel. This option is used to set the load
-          address for kernels used to capture crash dump on being kexec'ed
-          after panic. The default value for crash dump kernels is
-          0x1000000 (16MB). This can also be set based on the "X" value as
+          This gives the physical address where the kernel is loaded. It
+          should be aligned to 2MB boundary.
+
+          If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
+          bzImage will decompress itself to above physical address and
+          run from there. Otherwise, bzImage will run from the address where
+          it has been loaded by the boot loader and will ignore above physical
+          address.
+
+          In normal kdump cases one does not have to set/change this option
+          as now bzImage can be compiled as a completely relocatable image
+          (CONFIG_RELOCATABLE=y) and be used to load and run from a different
+          address. This option is mainly useful for the folks who don't want
+          to use a bzImage for capturing the crash dump and want to use a
+          vmlinux instead.
+
+          So if you are using bzImage for capturing the crash dump, leave
+          the value here unchanged to 0x200000 and set CONFIG_RELOCATABLE=y.
+          Otherwise if you plan to use vmlinux for capturing the crash dump
+          change this value to start of the reserved region (Typically 16MB
+          0x1000000). In other words, it can be set based on the "X" value as
           specified in the "crashkernel=YM@XM" command line boot parameter
           passed to the panic-ed kernel. Typically this parameter is set as
           crashkernel=64M@16M. Please take a look at
           Documentation/kdump/kdump.txt for more details about crash dumps.
 
+          Usage of bzImage for capturing the crash dump is advantageous as
+          one does not have to build two kernels. Same kernel can be used
+          as production kernel and capture kernel.
+
           Don't change this unless you know what you are doing.
 
 config SECCOMP