From: Kornel Dulęba Date: Thu, 17 Apr 2025 11:47:54 +0000 (+0000) Subject: arm64: Support ARM64_VA_BITS=52 when setting ARCH_MMAP_RND_BITS_MAX X-Git-Tag: v6.16-rc1~133^2~5^2~18 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f101c56447717c595d803894ba0e215f56c6fba4;p=thirdparty%2Fkernel%2Flinux.git arm64: Support ARM64_VA_BITS=52 when setting ARCH_MMAP_RND_BITS_MAX When the 52-bit virtual addressing was introduced the select like ARCH_MMAP_RND_BITS_MAX logic was never updated to account for it. Because of that the rnd max bits knob is set to the default value of 18 when ARM64_VA_BITS=52. Fix this by setting ARCH_MMAP_RND_BITS_MAX to the same value that would be used if 48-bit addressing was used. Higher values can't used here because 52-bit addressing is used only if the caller provides a hint to mmap, with a fallback to 48-bit. The knob in question is an upper bound for what the user can set in /proc/sys/vm/mmap_rnd_bits, which in turn is used to determine how many random bits can be inserted into the base address used for mmap allocations. Since 48-bit allocations are legal with ARM64_VA_BITS=52, we need to make sure that the base address is small enough to facilitate this. Fixes: b6d00d47e81a ("arm64: mm: Introduce 52-bit Kernel VAs") Signed-off-by: Kornel Dulęba Reviewed-by: Anshuman Khandual Link: https://lore.kernel.org/r/20250417114754.3238273-1-korneld@google.com Signed-off-by: Will Deacon --- diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index a182295e6f08b..6527d0d5656a1 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -333,9 +333,9 @@ config ARCH_MMAP_RND_BITS_MAX default 24 if ARM64_VA_BITS=39 default 27 if ARM64_VA_BITS=42 default 30 if ARM64_VA_BITS=47 - default 29 if ARM64_VA_BITS=48 && ARM64_64K_PAGES - default 31 if ARM64_VA_BITS=48 && ARM64_16K_PAGES - default 33 if ARM64_VA_BITS=48 + default 29 if (ARM64_VA_BITS=48 || ARM64_VA_BITS=52) && ARM64_64K_PAGES + default 31 if (ARM64_VA_BITS=48 || ARM64_VA_BITS=52) && ARM64_16K_PAGES + default 33 if (ARM64_VA_BITS=48 || ARM64_VA_BITS=52) default 14 if ARM64_64K_PAGES default 16 if ARM64_16K_PAGES default 18