Messages in this thread | | | Date | Fri, 26 Aug 2022 19:08:23 +0800 | Subject | Re: [PATCH] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually | From | Liu Song <> |
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> On Fri, Aug 05, 2022 at 05:21:14PM +0800, Liu Song wrote: >> From: Liu Song <liusong@linux.alibaba.com> >> >> 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> >> --- >> arch/arm64/kernel/proton-pack.c | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c >> index 40be3a7..bd16903 100644 >> --- a/arch/arm64/kernel/proton-pack.c >> +++ b/arch/arm64/kernel/proton-pack.c >> @@ -988,6 +988,14 @@ static void this_cpu_set_vectors(enum arm64_bp_harden_el1_vectors slot) >> 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; >> @@ -1001,7 +1009,7 @@ 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; > It would be good to have an Ack (or a shrug) from somebody @arm.com on this > one. > > Other than that, the documentation needs updating for the new option.
Thanks for the reminder, I will post another V2 version.
Thanks
> > Will
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