From 5a4c2a314083b07751c3151baf5e6ed7cc3aba36 Mon Sep 17 00:00:00 2001 From: Kefeng Wang Date: Wed, 4 Jan 2023 21:00:00 +0800 Subject: [PATCH] arm64: make ARCH_FORCE_MAX_ORDER selectable The other architectures with ARCH_FORCE_MAX_ORDER are selectable, but not for ARM64, this is to make it selectable on ARM64, which is useful for user that need to allocate more than 4MB of physically contiguous memory with 4K pagesize, also bigger on 16K pagesize too, the max value of MAX_ORDER is calculated bellow, see include/linux/mmzone.h, MAX_ORDER - 1 + PAGE_SHIFT <= SECTION_SIZE_BITS so max value of MAX_ORDER = SECTION_SIZE_BITS + 1 - PAGE_SHIFT | SECTION_SIZE_BITS | PAGE_SHIFT | max MAX_ORDER | default MAX_ORDER | ----+-------------------+--------------+-----------------+--------------------+ 4K | 27 | 12 | 16 | 11 | 16K | 27 | 14 | 14 | 12 | 64K | 29 | 16 | 14 | 14 | ----+-------------------+--------------+-----------------+--------------------+ Signed-off-by: Kefeng Wang Link: https://lore.kernel.org/r/20230104130000.69806-1-wangkefeng.wang@huawei.com [catalin.marinas@arm.com: add the calculations as comment to arch/arm64/Kconfig] Signed-off-by: Catalin Marinas --- arch/arm64/Kconfig | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 03934808b2ed0..8cfd8dcf7e755 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1456,10 +1456,23 @@ config XEN help Say Y if you want to run Linux in a Virtual Machine on Xen on ARM64. +# include/linux/mmzone.h requires the following to be true: +# +# MAX_ORDER - 1 + PAGE_SHIFT <= SECTION_SIZE_BITS +# +# so the maximum value of MAX_ORDER is SECTION_SIZE_BITS + 1 - PAGE_SHIFT: +# +# | SECTION_SIZE_BITS | PAGE_SHIFT | max MAX_ORDER | default MAX_ORDER | +# ----+-------------------+--------------+-----------------+--------------------+ +# 4K | 27 | 12 | 16 | 11 | +# 16K | 27 | 14 | 14 | 12 | +# 64K | 29 | 16 | 14 | 14 | config ARCH_FORCE_MAX_ORDER - int + int "Maximum zone order" if ARM64_4K_PAGES || ARM64_16K_PAGES default "14" if ARM64_64K_PAGES + range 12 14 if ARM64_16K_PAGES default "12" if ARM64_16K_PAGES + range 11 16 if ARM64_4K_PAGES default "11" help The kernel memory allocator divides physically contiguous memory -- 2.30.2