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Message-Id: <20240716085136.4160-1-chanho.min@lge.com> Date: Tue, 16 Jul 2024 17:51:36 +0900 From: Chanho Min <chanho.min@....com> To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org> Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Gunho Lee <gunho.lee@....com>, Chanho Min <chanho.min@....com> Subject: [PATCH] arm64: set MITIGATE_SPECTRE_BRANCH_HISTORY to n by default lmbench shows 25% performance regression after MITIGATE_SPECTRE_BRANCH_HISTORY is enabled. This performance drop may be more significant than mitigating the spectre-BHB. This patch changes this security option to disable by default and makes it selectable. - lat_syscall result with MITIGATE_SPECTRE_BRANCH_HISTORY enabled (cortex-a78) write call 0.2777 0.2810 0.2824 0.280367 read call 0.3435 0.3452 0.3443 0.344333 - lat_syscall result with MITIGATE_SPECTRE_BRANCH_HISTORY disabled (cortex-a78) write call 0.2101 0.2117 0.2116 0.2111 read call 0.2732 0.2744 0.2763 0.274633 Signed-off-by: Chanho Min <chanho.min@....com> --- arch/arm64/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 5d91259ee7b5..be76f425c060 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1626,7 +1626,7 @@ config UNMAP_KERNEL_AT_EL0 config MITIGATE_SPECTRE_BRANCH_HISTORY bool "Mitigate Spectre style attacks against branch history" if EXPERT - default y + default n help Speculation attacks against some high-performance processors can make use of branch history to influence future speculation. -- 2.17.1
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