From: Will Deacon <will@kernel.org>
To: "Catalin Marinas" <catalin.marinas@arm.com>,
"Kornel Dulęba" <korneld@google.com>
Cc: kernel-team@android.com, Will Deacon <will@kernel.org>,
Steve Capper <steve.capper@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, ssradjacoumar@google.com,
chromeos-krk-upstreaming@google.com,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH v2] arm64: Support ARM64_VA_BITS=52 when setting ARCH_MMAP_RND_BITS_MAX
Date: Tue, 29 Apr 2025 21:27:48 +0100 [thread overview]
Message-ID: <174593987866.472512.6873137326879401537.b4-ty@kernel.org> (raw)
In-Reply-To: <20250417114754.3238273-1-korneld@google.com>
On Thu, 17 Apr 2025 11:47:54 +0000, Kornel Dulęba wrote:
> 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.
>
> [...]
Applied to arm64 (for-next/mm), thanks!
[1/1] arm64: Support ARM64_VA_BITS=52 when setting ARCH_MMAP_RND_BITS_MAX
https://git.kernel.org/arm64/c/f101c5644771
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
prev parent reply other threads:[~2025-04-29 20:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-17 11:47 Kornel Dulęba
2025-04-29 20:27 ` Will Deacon [this message]
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