Commit 4632cb22 authored by Mike Rapoport (IBM)'s avatar Mike Rapoport (IBM) Committed by Andrew Morton
Browse files

arm64: reword ARCH_FORCE_MAX_ORDER prompt and help text 

The prompt and help text of ARCH_FORCE_MAX_ORDER are not even close to
describe this configuration option.

Update both to actually describe what this option does.

[rppt@kernel.org: change ARCH_FORCE_MAX_ORDER dependencies]
  Link: https://lkml.kernel.org/r/20230325060828.2662773-4-rppt@kernel.org
Link: https://lkml.kernel.org/r/20230324052233.2654090-4-rppt@kernel.org


Signed-off-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Reviewed-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Miller <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Rich Felker <dalias@libc.org>
Cc: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 34affcd7

arch/arm64/Kconfig

+12 −12
Original line number Diff line number Diff line
@@ -1487,24 +1487,24 @@ config XEN 
# 16K |       27          |      14      |       13        |         11         |

# 64K |       29          |      16      |       13        |         13         |

config ARCH_FORCE_MAX_ORDER

	int "Maximum zone order" if EXPERT && (ARM64_4K_PAGES || ARM64_16K_PAGES)

	int "Order of maximal physically contiguous allocations" if EXPERT && (ARM64_4K_PAGES || ARM64_16K_PAGES)

	default "13" if ARM64_64K_PAGES

	default "11" if ARM64_16K_PAGES

	default "10"

	help

	  The kernel memory allocator divides physically contiguous memory

	  blocks into "zones", where each zone is a power of two number of

	  pages.  This option selects the largest power of two that the kernel

	  keeps in the memory allocator.  If you need to allocate very large

	  blocks of physically contiguous memory, then you may need to

	  increase this value.

	  The kernel page allocator limits the size of maximal physically

	  contiguous allocations. The limit is called MAX_ORDER and it

	  defines the maximal power of two of number of pages that can be

	  allocated as a single contiguous block. This option allows

	  overriding the default setting when ability to allocate very

	  large blocks of physically contiguous memory is required.



	  We make sure that we can allocate up to a HugePage size for each configuration.

	  Hence we have :

		MAX_ORDER = PMD_SHIFT - PAGE_SHIFT  => PAGE_SHIFT - 3

	  The maximal size of allocation cannot exceed the size of the

	  section, so the value of MAX_ORDER should satisfy



	  However for 4K, we choose a higher default value, 10 as opposed to 9, giving us

	  4M allocations matching the default size used by generic code.

	    MAX_ORDER + PAGE_SHIFT <= SECTION_SIZE_BITS



	  Don't change if unsure.



config UNMAP_KERNEL_AT_EL0

	bool "Unmap kernel when running in userspace (aka \"KAISER\")" if EXPERT