5.15-stable review patch. If anyone has any objections, please let me know.
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From: Liu Song liusong@linux.alibaba.com
[ 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 liusong@linux.alibaba.com Acked-by: Catalin Marinas catalin.marinas@arm.com Link: https://lore.kernel.org/r/1661514050-22263-1-git-send-email-liusong@linux.al... Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Pu Lehui pulehui@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/admin-guide/kernel-parameters.txt | 5 +++++ arch/arm64/kernel/proton-pack.c | 10 +++++++++- 2 files changed, 14 insertions(+), 1 deletion(-)
--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3105,6 +3105,7 @@ spectre_bhi=off [X86] spectre_v2_user=off [X86] ssbd=force-off [ARM64] + nospectre_bhb [ARM64] tsx_async_abort=off [X86]
Exceptions: @@ -3526,6 +3527,10 @@ 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
--- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -1023,6 +1023,14 @@ static void this_cpu_set_vectors(enum ar isb(); }
+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) { bp_hardening_cb_t cpu_cb; @@ -1036,7 +1044,7 @@ void spectre_bhb_enable_mitigation(const /* 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;