Messages in this thread | | | Subject | Re: [PATCH v5 01/10] arm64: Provide a command line to disable spectre_v2 mitigation | From | Suzuki K Poulose <> | Date | Thu, 28 Feb 2019 18:25:46 +0000 |
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On 28/02/2019 18:21, Catalin Marinas wrote: > On Thu, Feb 28, 2019 at 06:14:34PM +0000, Suzuki K Poulose wrote: >> On 27/02/2019 01:05, Jeremy Linton wrote: >>> There are various reasons, including bencmarking, to disable spectrev2 >>> mitigation on a machine. Provide a command-line to do so. >>> >>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> >>> Cc: Jonathan Corbet <corbet@lwn.net> >>> Cc: linux-doc@vger.kernel.org >> >> >>> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c >>> index 9950bb0cbd52..d2b2c69d31bb 100644 >>> --- a/arch/arm64/kernel/cpu_errata.c >>> +++ b/arch/arm64/kernel/cpu_errata.c >>> @@ -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; >>> + } >>> + >> >> Could we not disable the "cap" altogether instead, rather than disabling the >> work around ? Or do we need that information ? > > There are a few ideas here but I think we settled on always reporting in > sysfs even if the mitigation is disabled in .config. So I guess we need > the "cap" around for the reporting part. >
Thanks Catalin.
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
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