6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kornel Dulęba korneld@google.com
[ Upstream commit f101c56447717c595d803894ba0e215f56c6fba4 ]
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 korneld@google.com Reviewed-by: Anshuman Khandual anshuman.khandual@arm.com Link: https://lore.kernel.org/r/20250417114754.3238273-1-korneld@google.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/Kconfig | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 658c6a61ab6fb..4ecba0690938c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -304,9 +304,9 @@ 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