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arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually

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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.alibaba.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Liu Song 2022-08-26 19:40:50 +08:00 committed by Catalin Marinas
parent 8eb858c44b
commit 877ace9eab
2 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/admin-guide/kernel-parameters.txt
View File

@ -3207,6 +3207,7 @@
spectre_v2_user=off [X86]
spec_store_bypass_disable=off [X86,PPC]
ssbd=force-off [ARM64]
nospectre_bhb [ARM64]
l1tf=off [X86]
mds=off [X86]
tsx_async_abort=off [X86]
@ -3631,6 +3632,10 @@
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

10
arch/arm64/kernel/proton-pack.c
View File

@ -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;