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@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Cc: douly.fnst@cn.fujitsu.com
Cc: dyoung@redhat.com
Cc: m.mizuma@jp.fujitsu.com
Link: http://lkml.kernel.org/r/1494654390-23861-4-git-send-email-bhe@redhat.com
[ Various spelling fixes. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 15f79c2..4e4c340 100644 (file)
--- 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.