1 files changed, 24 insertions, 5 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 722a74161246..766087781ecd 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1640,15 +1640,30 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         that the amount of memory usable for all allocations
                         is not too small.
 
+        movablemem_map=acpi
+                        [KNL,X86,IA-64,PPC] This parameter is similar to
+                        memmap except it specifies the memory map of
+                        ZONE_MOVABLE.
+                        This option inform the kernel to use Hot Pluggable bit
+                        in flags from SRAT from ACPI BIOS to determine which
+                        memory devices could be hotplugged. The corresponding
+                        memory ranges will be set as ZONE_MOVABLE.
+                        NOTE: Whatever node the kernel resides in will always
+                              be un-hotpluggable.
+
         movablemem_map=nn[KMG]@ss[KMG]
                         [KNL,X86,IA-64,PPC] This parameter is similar to
                         memmap except it specifies the memory map of
                         ZONE_MOVABLE.
-                        If more areas are all within one node, then from
-                        lowest ss to the end of the node will be ZONE_MOVABLE.
-                        If an area covers two or more nodes, the area from
-                        ss to the end of the 1st node will be ZONE_MOVABLE,
-                        and all the rest nodes will only have ZONE_MOVABLE.
+                        If user specifies memory ranges, the info in SRAT will
+                        be ingored. And it works like the following:
+                        - If more ranges are all within one node, then from
+                          lowest ss to the end of the node will be ZONE_MOVABLE.
+                        - If a range is within a node, then from ss to the end
+                          of the node will be ZONE_MOVABLE.
+                        - If a range covers two or more nodes, then from ss to
+                          the end of the 1st node will be ZONE_MOVABLE, and all
+                          the rest nodes will only have ZONE_MOVABLE.
                         If memmap is specified at the same time, the
                         movablemem_map will be limited within the memmap
                         areas. If kernelcore or movablecore is also specified,
@@ -1656,6 +1671,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         satisfied. So the administrator should be careful that
                         the amount of movablemem_map areas are not too large.
                         Otherwise kernel won't have enough memory to start.
+                        NOTE: We don't stop users specifying the node the
+                              kernel resides in as hotpluggable so that this
+                              option can be used as a workaround of firmware
+                              bugs.
 
         MTD_Partition=  [MTD]
                         Format: <name>,<region-number>,<size>,<offset>