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arm64: Provide a command line to disable spectre_v2 mitigation 

There are various reasons, such as benchmarking, to disable spectrev2
mitigation on a machine. Provide a command-line option to do so.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Jeremy Linton 2019-04-15 16:21:20 -05:00 committed by Will Deacon
parent cbafee55b5
commit e5ce5e7267
2 changed files with 17 additions and 4 deletions
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8
Documentation/admin-guide/kernel-parameters.txt
View File

@ -2905,10 +2905,10 @@
check bypass). With this option data leaks are possible
in the system.
nospectre_v2 [X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2
(indirect branch prediction) vulnerability. System may
allow data leaks with this option, which is equivalent
to spectre_v2=off.
nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
the Spectre variant 2 (indirect branch prediction)
vulnerability. System may allow data leaks with this
option.
nospec_store_bypass_disable
[HW] Disable all mitigations for the Speculative Store Bypass vulnerability

13
arch/arm64/kernel/cpu_errata.c
View File

@ -220,6 +220,14 @@ static void qcom_link_stack_sanitization(void)
: "=&r" (tmp));
}
static bool __nospectre_v2;
static int __init parse_nospectre_v2(char *str)
{
__nospectre_v2 = true;
return 0;
}
early_param("nospectre_v2", parse_nospectre_v2);
static void
enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
{
@ -231,6 +239,11 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
if (!entry->matches(entry, SCOPE_LOCAL_CPU))
return;
if (__nospectre_v2) {
pr_info_once("spectrev2 mitigation disabled by command line option\n");
return;
}
if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
return;