[tip:x86/boot] Documentation/kernel-parameters.txt: Update 'memmap=' boot option description

[tip-bot for Baoquan He]

Commit-ID:  8fcc9bc3eaa2ef8345e2b4b22e3a88804ac46337
Gitweb:     http://git.kernel.org/tip/8fcc9bc3eaa2ef8345e2b4b22e3a88804ac46337
Author:     Baoquan He <bhe@xxxxxxxxxx>
AuthorDate: Sat, 13 May 2017 13:46:30 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 24 May 2017 09:50:27 +0200

Documentation/kernel-parameters.txt: Update 'memmap=' boot 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 <bhe@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dan.j.williams@xxxxxxxxx
Cc: douly.fnst@xxxxxxxxxxxxxx
Cc: dyoung@xxxxxxxxxx
Cc: m.mizuma@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1494654390-23861-4-git-send-email-bhe@xxxxxxxxxx
[ Various spelling fixes. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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 15f79c2..4e4c340 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2127,6 +2127,12 @@
 	memmap=nn[KMG]@ss[KMG]
 			[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 is equivalent to mem=nn[KMG],
+			which limits max address to nn[KMG].
+			Multiple different regions can be specified,
+			comma delimited.
+			Example:
+				memmap=100M@2G,100M#3G,1G!1024G
 
 	memmap=nn[KMG]#ss[KMG]
 			[KNL,ACPI] Mark specific memory as ACPI data.
@@ -2139,6 +2145,9 @@
 			         memmap=64K$0x18690000
 			         or
 			         memmap=0x10000$0x18690000
+			Some bootloaders may need an escape character before '$',
+			like Grub2, otherwise '$' and the following number
+			will be eaten.
 
 	memmap=nn[KMG]!ss[KMG]
 			[KNL,X86] Mark specific memory as protected.