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Subject[PATCH v4 3/3] Documentation/kernel-parameters.txt: Update 'memmap=' option description
In commit:

9710f581bb4c ("x86, mm: Let "memmap=" take more entries one time")

... 'memmap=' was changed to adopt multiple, comma delimited values in a
single entry, so update the related description.

In the special case of only specifying size value without an offset,
like memmap=nn[KMG], memmap behaves similarly to mem=nn[KMG], so update
it too here.

Furthermore, for memmap=nn[KMG]$ss[KMG], an escape character needs be added
before '$' for some bootloaders. E.g in grub2, if we specify memmap=100M$5G
as suggested by the documentation, "memmap=100MG" gets passed to the kernel.

Clarify all this.

Signed-off-by: Baoquan He <>
Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e4c9e0e..8d37f26 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2112,6 +2112,12 @@
[KNL] Force usage of a specific region of memory.
Region of memory to be used is from ss to ss+nn.
+ If @ss[KMG] is omitted, it equals to mem=nn[KMG]
+ which limits max address as nn[KMG].
+ Multiple different options can be put into one entry
+ with comma delimited to save space:
+ Example:
+ memmap=100M@2G,100M#3G,1G!1024G

[KNL,ACPI] Mark specific memory as ACPI data.
@@ -2124,6 +2130,9 @@
+ Some bootloaders may need escape character before '$',
+ like in grub2, otherwise '$' and the following number
+ will be eaten.

[KNL,X86] Mark specific memory as protected.
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