The patch titled
Subject: memblock: improve MEMBLOCK_HOTPLUG documentation
has been added to the -mm tree. Its filename is
memblock-improve-memblock_hotplug-documentation.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/memblock-improve-memblock_hotplug-documentation.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/memblock-improve-memblock_hotplug-documentation.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: memblock: improve MEMBLOCK_HOTPLUG documentation
The description of MEMBLOCK_HOTPLUG is currently short and consequently
misleading: we're actually dealing with a memory region that might get
hotunplugged later (i.e., the platform+firmware supports it), yet it is
indicated in the firmware-provided memory map as system ram that will just
get used by the system for any purpose when not taking special care. The
firmware marked this memory region as a hot(un)plugged (e.g., hotplugged
before reboot), implying that it might get hotunplugged again later.
Whether we consider this information depends on the "movable_node" kernel
commandline parameter: only with "movable_node" set, we'll try keeping
this memory hotunpluggable, for example, by not serving early allocations
from this memory region and by letting the buddy manage it using the
ZONE_MOVABLE.
Let's make this clearer by extending the documentation.
Note: kexec *has to* indicate this memory to the second kernel. With
"movable_node" set, we don't want to place kexec-images on this memory.
Without "movable_node" set, we don't care and can place kexec-images on
this memory. In both cases, after successful memory hotunplug, kexec has
to be re-armed to update the memory map for the second kernel and to place
the kexec-images somewhere else.
Link: https://lkml.kernel.org/r/20211004093605.5830-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: Jianyong Wu <Jianyong.Wu@xxxxxxx>
Cc: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Shahab Vahedi <shahab@xxxxxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memblock.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/include/linux/memblock.h~memblock-improve-memblock_hotplug-documentation
+++ a/include/linux/memblock.h
@@ -28,7 +28,11 @@ extern unsigned long long max_possible_p
/**
* enum memblock_flags - definition of memory region attributes
* @MEMBLOCK_NONE: no special request
- * @MEMBLOCK_HOTPLUG: hotpluggable region
+ * @MEMBLOCK_HOTPLUG: memory region indicated in the firmware-provided memory
+ * map during early boot as hot(un)pluggable system RAM (e.g., memory range
+ * that might get hotunplugged later). With "movable_node" set on the kernel
+ * commandline, try keeping this memory region hotunpluggable. Does not apply
+ * to memblocks added ("hotplugged") after early boot.
* @MEMBLOCK_MIRROR: mirrored region
* @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
* reserved in the memory map; refer to memblock_mark_nomap() description
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
memory-hotplugrst-fix-two-instances-of-movablecore-that-should-be-movable_node.patch
memory-hotplugrst-fix-wrong-sys-module-memory_hotplug-parameters-path.patch
memory-hotplugrst-document-the-auto-movable-online-policy.patch
mm-memory_hotplug-remove-config_x86_64_acpi_numa-dependency-from-config_memory_hotplug.patch
mm-memory_hotplug-remove-config_memory_hotplug_sparse.patch
mm-memory_hotplug-restrict-config_memory_hotplug-to-64-bit.patch
mm-memory_hotplug-remove-highmem-leftovers.patch
mm-memory_hotplug-remove-stale-function-declarations.patch
x86-remove-memory-hotplug-support-on-x86_32.patch
mm-memory_hotplug-handle-memblock_add_node-failures-in-add_memory_resource.patch
memblock-improve-memblock_hotplug-documentation.patch
memblock-allow-to-specify-flags-with-memblock_add_node.patch
memblock-add-memblock_driver_managed-to-mimic-ioresource_sysram_driver_managed.patch
mm-memory_hotplug-indicate-memblock_driver_managed-with-ioresource_sysram_driver_managed.patch
x86-xen-update-xen_oldmem_pfn_is_ram-documentation.patch
x86-xen-simplify-xen_oldmem_pfn_is_ram.patch
x86-xen-print-a-warning-when-hvmop_get_mem_type-fails.patch
proc-vmcore-let-pfn_is_ram-return-a-bool.patch
proc-vmcore-convert-oldmem_pfn_is_ram-callback-to-more-generic-vmcore-callbacks.patch
virtio-mem-factor-out-hotplug-specifics-from-virtio_mem_init-into-virtio_mem_init_hotplug.patch
virtio-mem-factor-out-hotplug-specifics-from-virtio_mem_probe-into-virtio_mem_init_hotplug.patch
virtio-mem-factor-out-hotplug-specifics-from-virtio_mem_remove-into-virtio_mem_deinit_hotplug.patch
virtio-mem-kdump-mode-to-sanitize-proc-vmcore-access.patch
kernel-resource-clean-up-and-optimize-iomem_is_exclusive.patch
kernel-resource-disallow-access-to-exclusive-system-ram-regions.patch
virtio-mem-disallow-mapping-virtio-mem-memory-via-dev-mem.patch
