From: Catalin Marinas <catalin.marinas@arm.com>
To: "Pierre-Clément Tosi" <ptosi@google.com>
Cc: will@kernel.org, suzuki.poulose@arm.com, maz@kernel.org,
corbet@lwn.net, yee.lee@mediatek.com, ascull@google.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH] arm64: Optionally disable EL0 MTE via command-line
Date: Tue, 17 Feb 2026 10:51:24 +0000 [thread overview]
Message-ID: <aZRIHZ2Wq81S-FZY@arm.com> (raw)
In-Reply-To: <plslbeuzfag5dfizunxmhyw5axxbuz7r3jdlhjluzdwrm4rtzk@bm5xmxzmy6v3>
On Fri, Feb 13, 2026 at 12:51:07PM +0100, Pierre-Clément Tosi wrote:
> Although it is currently possible to fully disable MTE on MTE-capable
> CPUs (with arm64.nomte or id_aa64pfr1.mte=0) and to only use MTE in
> userspace (with kasan=off), there is no way to limit the use of MTE to
> the kernel because CPU capabilities are traditionally exposed directly
> to userspace.
>
> To address this, introduce a new cmdline argument (inspired by the
> existing arm64.nomte) to only expose the MTE capability of the CPU to
> the kernel. Combined with KASAN, this results in only the kernel using
> the feature, while HWCAP2_MTE and the corresponding MSR ID_AA64PFR1_EL1
> field are hidden from userspace.
[...]
> + arm64.nomte_el0 [ARM64] Unconditionally disable Memory Tagging Extension
> + support for userspace
Why would we need this? It's a user-space choice whether it uses MTE or
not. It's not like the kernel is forcing it onto the user processes.
--
Catalin
next prev parent reply other threads:[~2026-02-17 10:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-13 11:51 [PATCH] arm64: Optionally disable EL0 MTE via command-line Pierre-Clément Tosi
2026-02-17 10:51 ` Catalin Marinas [this message]
2026-02-17 11:20 ` Pierre-Clément Tosi
2026-02-17 12:03 ` Will Deacon
2026-02-17 12:31 ` Pierre-Clément Tosi
2026-02-17 15:16 ` Will Deacon
2026-02-17 13:00 ` Marc Zyngier
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