linux-kernel - [PATCH v5 3/3] Documentation/kernel-parameters.txt: Update 'memmap=' option description

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Date:   Sat, 13 May 2017 13:46:30 +0800
From:   Baoquan He <bhe@...hat.com>
To:     tglx@...utronix.de, keescook@...omium.org, mingo@...nel.org,
        m.mizuma@...fujitsu.com
Cc:     linux-kernel@...r.kernel.org, dyoung@...hat.com,
        douly.fnst@...fujitsu.com, dan.j.williams@...el.com, hpa@...or.com,
        x86@...nel.org, Baoquan He <bhe@...hat.com>
Subject: [PATCH v5 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 <bhe@...hat.com>
---
 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..60d69aa 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 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
 
 	memmap=nn[KMG]#ss[KMG]
 			[KNL,ACPI] Mark specific memory as ACPI data.
@@ -2139,6 +2145,9 @@
 			         memmap=64K$0x18690000
 			         or
 			         memmap=0x10000$0x18690000
+			Some bootloaders may need escape character before '$',
+			like in grub2, otherwise '$' and the following number
+			will be eaten.
 
 	memmap=nn[KMG]!ss[KMG]
 			[KNL,X86] Mark specific memory as protected.
-- 
2.5.5