From: Liu Song <liusong@linux.alibaba.com>
To: liusong@linux.alibaba.com
Cc: catalin.marinas@arm.com, james.morse@arm.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, will@kernel.org
Subject: [PATCH v2] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually
Date: Fri, 26 Aug 2022 20:44:45 +0800 [thread overview]
Message-ID: <1661517885-112909-1-git-send-email-liusong@linux.alibaba.com> (raw)
In-Reply-To: <837426e9-0f24-2ce2-e631-b91276035397@linux.alibaba.com>
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>
---
Documentation/admin-guide/kernel-parameters.txt | 5 +++++
arch/arm64/kernel/proton-pack.c | 10 +++++++++-
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d7f3090..1edc9a6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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
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;
--
1.8.3.1
next prev parent reply other threads:[~2022-08-26 12:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-05 9:21 [PATCH] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually Liu Song
2022-08-25 15:25 ` Liu Song
2022-08-26 10:39 ` Will Deacon
2022-08-26 11:08 ` Liu Song
2022-08-26 12:44 ` Liu Song [this message]
2022-08-26 11:40 [PATCH v2] " Liu Song
2022-09-07 14:29 ` Catalin Marinas
2022-09-07 16:29 ` Will Deacon
2022-09-09 18:08 ` Catalin Marinas
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