From: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>

This kernel parameter allows to change the padding used
for the physical memory mapping section when KASLR
memory is enabled.

For memory hotplug capable systems, the default padding size,
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING, may not be enough.
The option is useful to adjust the padding size.

Signed-off-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>
---
 .../admin-guide/kernel-parameters.txt          | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f4..4c4c5e6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3529,6 +3529,24 @@
                        fully seed the kernel's CRNG. Default is controlled
                        by CONFIG_RANDOM_TRUST_CPU.
 
+       rand_mem_physical_padding=
+                       [KNL] Define the padding size in terabytes
+                       used for the physical memory mapping section
+                       when KASLR is enabled.
+                       If the padding size is not enough, you can see
+                       'Set rand_mem_physical_padding=XX ...' in system
+                       boot message, so set the parameter as the message.
+
+                       This parameter is useful for the memory hot-add capable
+                       system. Such system may have more space than
+                       actual memory size to hot-add memory. If the
+                       padding size is not enough and a memory is hot-added,
+                       the hot-adding will fail because it destroys the
+                       system memory map. So, the padding size is needed to
+                       adjust in such system.
+                       The default value is
+                       CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING.
+
        ras=option[,option,...] [KNL] RAS-specific options
 
                cec_disable     [X86]
-- 
2.18.0

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