Commit e5ce5e72 authored by Jeremy Linton's avatar Jeremy Linton Committed by Will Deacon
Browse files

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: default avatarJeremy Linton <jeremy.linton@arm.com>
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: default avatarAndre Przywara <andre.przywara@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Tested-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent cbafee55

Documentation/admin-guide/kernel-parameters.txt

+4 −4
Original line number Original line Diff line number Diff line
@@ -2905,10 +2905,10 @@ 
			check bypass). With this option data leaks are possible

			check bypass). With this option data leaks are possible

			in the system.

			in the system.





	nospectre_v2	[X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2

	nospectre_v2	[X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for

			(indirect branch prediction) vulnerability. System may

			the Spectre variant 2 (indirect branch prediction)

			allow data leaks with this option, which is equivalent

			vulnerability. System may allow data leaks with this

			to spectre_v2=off.

			option.





	nospec_store_bypass_disable

	nospec_store_bypass_disable

			[HW] Disable all mitigations for the Speculative Store Bypass vulnerability

			[HW] Disable all mitigations for the Speculative Store Bypass vulnerability

arch/arm64/kernel/cpu_errata.c

+13 −0
Original line number Original line Diff line number Diff line
@@ -220,6 +220,14 @@ static void qcom_link_stack_sanitization(void) 
		     : "=&r" (tmp));

		     : "=&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

static void

enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)

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))

	if (!entry->matches(entry, SCOPE_LOCAL_CPU))

		return;

		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)

	if (psci_ops.smccc_version == SMCCC_VERSION_1_0)

		return;

		return;

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