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| author | David Hildenbrand <david@redhat.com> | 2021-11-05 23:44:46 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-11-06 23:30:42 +0300 |
| commit | e14b41556d9ec20af60a9f672ac6f64dd450763c (patch) | |
| tree | aeea89afb1b7819929bba39994629ebc6381fa26 /include | |
| parent | 53d38316ab2017a7c0d733765b521700aa357ec9 (diff) | |
| download | linux-e14b41556d9ec20af60a9f672ac6f64dd450763c.tar.xz | |
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@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Jianyong Wu <Jianyong.Wu@arm.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Shahab Vahedi <shahab@synopsys.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/memblock.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/memblock.h b/include/linux/memblock.h index 484650681bee..1d2b3e902a84 100644 --- a/include/linux/memblock.h +++ b/include/linux/memblock.h @@ -28,7 +28,11 @@ extern unsigned long long max_possible_pfn; /** * 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 |