[PATCH 0/8] implement "memmap on memory" feature on s390

Sumanth Korikkar
2023-11-14T18:03:08Z

Hi All,

The patch series implements "memmap on memory" feature on s390 and
provides the necessary fixes for it.

Patch 1 addresses the locking order in memory hotplug operations,
ensuring that the mem_hotplug_lock is held during critical operations
like mhp_init_memmap_on_memory() and mhp_deinit_memmap_on_memory()

Patch 2 deals with error handling in add_memory_resource() and considers
the possibility of altmap support. This ensures proper deallocation of
struct pages, aligning with the allocation strategy.

Patch 3 relocates the vmem_altmap code to sparse-vmemmap.c, enabling the
utilization of vmem_altmap_free() and vmem_altmap_offset() without the
dependency on CONFIG_ZONE_DEVICE. Note: These functions are also used in
arm64 architecture. However, ZONE_DEVICE or ARCH_HAS_ZONE_DEVICE doesnt
seems to be enabled in arm64.

Patch 4 introduces MEM_PHYS_ONLINE/OFFLINE memory notifiers. It
facilitates the emulation of dynamic ACPI event-triggered logic for
memory hotplug on platforms lacking such events. This sets the stage for
implementing the "memmap on memory" feature for s390 in subsequent
patches. All architecture/codepaths have the default cases handled in
memory notifiers. Hence, introducing new memory notifiers will have no
functional impact.

Patches 5 allocates vmemmap pages from self-contained memory range for
s390. It allocates memory map (struct pages array) from the hotplugged
memory range, rather than using system memory by passing altmap to
vmemmap functions.

Patch 6 implements MEM_PHYS_ONLINE and MEM_PHYS_OFFLINE memory notifiers
on s390. It involves making the memory block physically accessible and
then calling __add_pages()/__remove_pages() with altmap parameter.

Patch 7 removes unhandled memory notifier types. This is currently
handled in default case

Patch 8 finally enables MHP_MEMMAP_ON_MEMORY on s390

Thank you

Sumanth Korikkar (8):
mm/memory_hotplug: fix memory hotplug locking order
mm/memory_hotplug: fix error handling in add_memory_resource()
mm: use vmem_altmap code without CONFIG_ZONE_DEVICE
mm/memory_hotplug: introduce MEM_PHYS_ONLINE/OFFLINE memory notifiers
s390/mm: allocate vmemmap pages from self-contained memory range
s390/mm: implement MEM_PHYS_ONLINE MEM_PHYS_OFFLINE memory notifiers
s390/sclp: remove unhandled memory notifier type
s390: enable MHP_MEMMAP_ON_MEMORY

arch/s390/Kconfig | 1 +
arch/s390/mm/init.c | 19 ++++++++---
arch/s390/mm/vmem.c | 62 ++++++++++++++++++++----------------
drivers/base/memory.c | 28 ++++++++++++++--
drivers/s390/char/sclp_cmd.c | 37 +++++++++++++++------
include/linux/memory.h | 2 ++
include/linux/memremap.h | 12 -------
include/linux/mm.h | 2 ++
mm/memory_hotplug.c | 15 ++++-----
mm/memremap.c | 14 +-------
mm/sparse-vmemmap.c | 13 ++++++++
11 files changed, 129 insertions(+), 76 deletions(-)

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2.41.0