[PATCH v2] docs/kernel-parameters: update description of mem=

Mike Rapoport
2022-03-09T17:23:09Z

From: Mike Rapoport <rppt@linux.ibm.com>

The existing description of mem= does not cover all the cases and
differences between how architectures treat it.

Extend the description to match the code.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
v1: https://lore.kernel.org/all/20220309122446.1118738-1-rppt@kernel.org
* drop clumsy and redundant paragraph about Hexagon

.../admin-guide/kernel-parameters.txt | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f5a27f067db9..40cd4136331b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2834,6 +2834,13 @@
2 when the kernel is not able to see the whole system memory;
3 memory that lies after 'mem=' boundary is excluded from
the hypervisor, then assigned to KVM guests.
+ 4 to limit the memory available for kdump kernel.
+
+ [ARC,MICROBLAZE] - the limit applies only to low memory,
+ high memory is not affected.
+
+ [ARM64] - only limits memory covered by the linear
+ mapping. The NOMAP regions are not affected.

[X86] Work as limiting max address. Use together
with memmap= to avoid physical address space collisions.
@@ -2844,6 +2851,17 @@
in above case 3, memory may need be hot added after boot
if system memory of hypervisor is not sufficient.

+ mem=nn[KMG]@ss[KMG]
+ [ARM,MIPS] - override the memory layout reported by
+ firmware.
+ Define a memory region of size nn[KMG] starting at
+ ss[KMG].
+ Multiple different regions can be specified with
+ multiple mem= parameters on the command line.
+
+ mem=nn[KMG] [HEXAGON] Set the memory size.
+ Must be specified, otherwise memory size will be 0.
+
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
memory.

--
2.34.1