linux-kernel - [RFC PATCH 2/8] arm64: Kconfig: fix ARCH_MMAP_RND_BITS

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Message-ID: <20241030101803.2037606-12-ardb+git@google.com>
Date: Wed, 30 Oct 2024 11:18:06 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Ryan Roberts <ryan.roberts@....com>, 
	Anshuman Khandual <anshuman.khandual@....com>, Kees Cook <keescook@...omium.org>
Subject: [RFC PATCH 2/8] arm64: Kconfig: fix ARCH_MMAP_RND_BITS_MAX for 52-bit
 virtual addressing

From: Ard Biesheuvel <ardb@...nel.org>

The default values for ARCH_MMAP_RND_BITS_MAX fail to take into account
that we now have support for 52-bit virtual addressing. As these configs
are compatible with hardware that is incapable of 52-bit virtual
addressing, use the same value we use for 47/48-bit virtual addressing.
(For the sake of simplicity, use the same value for 47 and 48 bit
virtual addressing for 16k pages)

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/Kconfig | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ec218ef22f2b..ac8e7550430b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -324,13 +324,9 @@ config ARCH_MMAP_RND_BITS_MAX
 	default 19 if ARM64_VA_BITS=36
 	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 14 if ARM64_64K_PAGES
-	default 16 if ARM64_16K_PAGES
-	default 18
+	default 29 if ARM64_64K_PAGES
+	default 30 if ARM64_16K_PAGES
+	default 33
 
 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 	default 7 if ARM64_64K_PAGES
-- 
2.47.0.163.g1226f6d8fa-goog