linux-kernel - [PATCH v3 3/3] Documentation/kernel-parameters.txt: Update 'memmap=' option description

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Message-Id: <1493201772-19084-4-git-send-email-bhe@redhat.com>
Date:   Wed, 26 Apr 2017 18:16:12 +0800
From:   Baoquan He <bhe@...hat.com>
To:     mingo@...nel.org, linux-kernel@...r.kernel.org
Cc:     keescook@...omium.org, dyoung@...hat.com,
        douly.fnst@...fujitsu.com, dan.j.williams@...el.com,
        Baoquan He <bhe@...hat.com>, Jonathan Corbet <corbet@....net>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-doc@...r.kernel.org
Subject: [PATCH v3 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>
Cc: Jonathan Corbet <corbet@....net>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-doc@...r.kernel.org
---
 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 986e443..d518144 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2097,6 +2097,12 @@
 	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.
@@ -2109,6 +2115,9 @@
 			         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