[RFC 0/3] mm/hotplug: Pre-validate the address range with platform

[Anshuman Khandual]

This series adds a mechanism allowing platforms to weigh in and prevalidate
incoming address range before proceeding further with the memory hotplug.
This helps prevent potential platform errors for the given address range,
down the hotplug call chain, which inevitably fails the hotplug itself.

This mechanism was suggested by David Hildenbrand during another discussion
with respect to a memory hotplug fix on arm64 platform.

https://lore.kernel.org/linux-arm-kernel/1600332402-30123-1-git-send-email-anshuman.khandual@arm.com/

This mechanism focuses on the addressibility aspect and not [sub] section
alignment aspect. Hence check_hotplug_memory_range() and check_pfn_span()
have been left unchanged. Wondering if all these can still be unified in
an expanded memhp_range_allowed() check, that can be called from multiple
memory hot add and remove paths.

This series applies on v5.10-rc5 and has been slightly tested on arm64.
But looking for some early feedback here.

Cc: Heiko Carstens <hca at linux.ibm.com>
Cc: Vasily Gorbik <gor at linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: David Hildenbrand <david at redhat.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-s390 at vger.kernel.org
Cc: linux-mm at kvack.org
Cc: linux-kernel at vger.kernel.org

Anshuman Khandual (3):
  mm/hotplug: Pre-validate the address range with platform
  arm64/mm: Define arch_get_addressable_range()
  s390/mm: Define arch_get_addressable_range()

 arch/arm64/include/asm/memory.h |  3 ++
 arch/arm64/mm/mmu.c             | 19 ++++++------
 arch/s390/include/asm/mmu.h     |  2 ++
 arch/s390/mm/vmem.c             | 16 ++++++++---
 include/linux/memory_hotplug.h  | 51 +++++++++++++++++++++++++++++++++
 mm/memory_hotplug.c             | 29 ++++++-------------
 mm/memremap.c                   |  9 +++++-
 7 files changed, 96 insertions(+), 33 deletions(-)

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2.20.1