linux-kernel - [PATCH 10/10] arm64: mops: allow disabling MOPS from the kernel command line

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Date:   Thu, 16 Feb 2023 16:00:12 +0000
From:   Kristina Martsenko <kristina.martsenko@....com>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Luis Machado <luis.machado@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 10/10] arm64: mops: allow disabling MOPS from the kernel command line

Make it possible to disable the MOPS extension at runtime using the
kernel command line. This can be useful for testing or working around
hardware issues.

Signed-off-by: Kristina Martsenko <kristina.martsenko@....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 6cfa6e3996cf..ee86fe17352d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -408,6 +408,9 @@
 	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
 			Extension support
 
+	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
+			Set instructions 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 d833d78a7f31..d13ae90042cb 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -123,6 +123,7 @@ static const struct ftr_set_desc isar2 __initconst = {
 	.fields		= {
 		FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
 		FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
+		FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
 		{}
 	},
 };
@@ -174,6 +175,7 @@ static const struct {
 	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
 	  "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
 	  "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0"	   },
+	{ "arm64.nomops",		"id_aa64isar2.mops=0" },
 	{ "arm64.nomte",		"id_aa64pfr1.mte=0" },
 	{ "nokaslr",			"kaslr.disabled=1" },
 };
-- 
2.25.1