linux-kernel - [PATCH 2/2] arm64/sme: Ensure that all fields in SMCR

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Message-Id: <20240213-arm64-fp-init-vec-cr-v1-2-7e7c2d584f26@kernel.org>
Date: Tue, 13 Feb 2024 15:32:46 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH 2/2] arm64/sme: Ensure that all fields in SMCR_EL1 are set
 to known values

At present nothing in our CPU initialisation code ever sets unknown fields
in SMCR_EL1 to known values, all updates to SMCR_EL1 are read/modify/write
sequences. All the unknown fields are RES0, explicitly initialise them as
such to avoid future surprises.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kernel/fpsimd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index cc3c9ad877a8..f96907b813fa 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1247,6 +1247,9 @@ void cpu_enable_sme(const struct arm64_cpu_capabilities *__always_unused p)
 	write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_SMEN_EL1EN, CPACR_EL1);
 	isb();
 
+	/* Ensure all bits in SMCR are set to known values */
+	write_sysreg_s(0, SYS_SMCR_EL1);
+
 	/* Allow EL0 to access TPIDR2 */
 	write_sysreg(read_sysreg(SCTLR_EL1) | SCTLR_ELx_ENTP2, SCTLR_EL1);
 	isb();

-- 
2.30.2