From: Liu Song Date: Sat, 7 Jun 2025 15:25:18 +0000 (+0000) Subject: arm64: spectre: increase parameters that can be used to turn off bhb mitigation indiv... X-Git-Tag: v5.10.239~22 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d38941ee87aa1e5848515f14cd61fa0e057ba512;p=thirdparty%2Fkernel%2Fstable.git arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually [ Upstream commit 877ace9eab7de032f954533afd5d1ecd0cf62eaf ] In our environment, it was found that the mitigation BHB has a great impact on the benchmark performance. For example, in the lmbench test, the "process fork && exit" test performance drops by 20%. So it is necessary to have the ability to turn off the mitigation individually through cmdline, thus avoiding having to compile the kernel by adjusting the config. Signed-off-by: Liu Song Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/1661514050-22263-1-git-send-email-liusong@linux.alibaba.com Signed-off-by: Catalin Marinas Signed-off-by: Pu Lehui Signed-off-by: Greg Kroah-Hartman --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 88110e74b3f7a..1eff151699830 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2954,6 +2954,7 @@ spec_store_bypass_disable=off [X86,PPC] spectre_v2_user=off [X86] ssbd=force-off [ARM64] + nospectre_bhb [ARM64] tsx_async_abort=off [X86] Exceptions: @@ -3367,6 +3368,10 @@ vulnerability. System may allow data leaks with this option. + nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch + history injection) vulnerability. System may allow data leaks + with this option. + nospec_store_bypass_disable [HW] Disable all mitigations for the Speculative Store Bypass vulnerability diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c index 223527066a4f7..7728026d98f75 100644 --- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -1088,6 +1088,13 @@ static void kvm_setup_bhb_slot(const char *hyp_vecs_start) { } #endif /* CONFIG_KVM */ static bool spectre_bhb_fw_mitigated; +static bool __read_mostly __nospectre_bhb; +static int __init parse_spectre_bhb_param(char *str) +{ + __nospectre_bhb = true; + return 0; +} +early_param("nospectre_bhb", parse_spectre_bhb_param); void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry) { @@ -1100,7 +1107,7 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry) /* No point mitigating Spectre-BHB alone. */ } else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) { pr_info_once("spectre-bhb mitigation disabled by compile time option\n"); - } else if (cpu_mitigations_off()) { + } else if (cpu_mitigations_off() || __nospectre_bhb) { pr_info_once("spectre-bhb mitigation disabled by command line option\n"); } else if (supports_ecbhb(SCOPE_LOCAL_CPU)) { state = SPECTRE_MITIGATED;