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From: <yee.lee@mediatek.com>
To: <linux-kernel@vger.kernel.org>
Cc: <nicholas.Tang@mediatek.com>, <Kuan-Ying.lee@mediatek.com>,
	<chinwen.chang@mediatek.com>, Yee Lee <yee.lee@mediatek.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Maciej W. Rozycki" <macro@orcam.me.uk>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Vlastimil Babka <vbabka@suse.cz>, Marc Zyngier <maz@kernel.org>,
	David Brazdil <dbrazdil@google.com>,
	Ard Biesheuvel <ardb@kernel.org>, Fuad Tabba <tabba@google.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
	<linux-arm-kernel@lists.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>
Subject: [PATCH v3 1/1] arm64/cpufeature: Optionally disable MTE via command-line
Date: Fri, 30 Jul 2021 22:49:53 +0800	[thread overview]
Message-ID: <20210730144957.30938-2-yee.lee@mediatek.com> (raw)
In-Reply-To: <20210730144957.30938-1-yee.lee@mediatek.com>

From: Yee Lee <yee.lee@mediatek.com>

For some low-end devices with limited resources,
MTE needs to be optionally disabled to save system
costs such as tag memory and firmware controls.

This allows ID_AA64PFR1_EL1.MTE to be overridden on 
its shadow value by giving "arm64.nomte" on cmdline,
and to suppress MTE feature.

Suggested-by: Marc Zyngier <maz@kernel.org>
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Yee Lee <yee.lee@mediatek.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/arm64/kernel/idreg-override.c              | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bdb22006f713..6f257e39d89e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -380,6 +380,9 @@
 	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
 			support
 
+	arm64.nomte	[ARM64] Unconditionally disable Memory Tagging Extension
+			support
+
 	ataflop=	[HW,M68k]
 
 	atarimouse=	[HW,MOUSE] Atari Mouse
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 53a381a7f65d..d8e606fe3c21 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -54,6 +54,7 @@ static const struct ftr_set_desc pfr1 __initconst = {
 	.override	= &id_aa64pfr1_override,
 	.fields		= {
 	        { "bt", ID_AA64PFR1_BT_SHIFT },
+		{ "mte", ID_AA64PFR1_MTE_SHIFT},
 		{}
 	},
 };
@@ -100,6 +101,7 @@ static const struct {
 	{ "arm64.nopauth",
 	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
 	  "id_aa64isar1.api=0 id_aa64isar1.apa=0"	   },
+	{ "arm64.nomte",		"id_aa64pfr1.mte=0" },
 	{ "nokaslr",			"kaslr.disabled=1" },
 };
 
-- 
2.18.0


  reply	other threads:[~2021-07-30 14:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 14:49 [PATCH v3 0/1] arm64/cpufeature: Support optionally disable MTE yee.lee
2021-07-30 14:49 ` yee.lee [this message]
2021-08-02 15:30   ` [PATCH v3 1/1] arm64/cpufeature: Optionally disable MTE via command-line Catalin Marinas
2021-08-03  5:55     ` Yee Lee
2021-11-25 10:19     ` Yee Lee
2021-12-03 16:33       ` Catalin Marinas
2021-12-14  8:19         ` Yee Lee
2021-12-14 12:02           ` Catalin Marinas

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