From a43ae4dfe56a01f5b98ba0cb2f784b6a43bafcc6 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 29 May 2018 13:11:09 +0100 Subject: arm64: Add 'ssbd' command-line option On a system where the firmware implements ARCH_WORKAROUND_2, it may be useful to either permanently enable or disable the workaround for cases where the user decides that they'd rather not get a trap overhead, and keep the mitigation permanently on or off instead of switching it on exception entry/exit. In any case, default to the mitigation being enabled. Reviewed-by: Julien Grall Reviewed-by: Mark Rutland Acked-by: Will Deacon Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas --- arch/arm64/kernel/cpu_errata.c | 103 ++++++++++++++++++++++++++++++++++------- 1 file changed, 87 insertions(+), 16 deletions(-) (limited to 'arch/arm64/kernel') diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 7e8f12d85d99..1075f90fdd8c 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -235,6 +235,38 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry) #ifdef CONFIG_ARM64_SSBD DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required); +int ssbd_state __read_mostly = ARM64_SSBD_KERNEL; + +static const struct ssbd_options { + const char *str; + int state; +} ssbd_options[] = { + { "force-on", ARM64_SSBD_FORCE_ENABLE, }, + { "force-off", ARM64_SSBD_FORCE_DISABLE, }, + { "kernel", ARM64_SSBD_KERNEL, }, +}; + +static int __init ssbd_cfg(char *buf) +{ + int i; + + if (!buf || !buf[0]) + return -EINVAL; + + for (i = 0; i < ARRAY_SIZE(ssbd_options); i++) { + int len = strlen(ssbd_options[i].str); + + if (strncmp(buf, ssbd_options[i].str, len)) + continue; + + ssbd_state = ssbd_options[i].state; + return 0; + } + + return -EINVAL; +} +early_param("ssbd", ssbd_cfg); + void __init arm64_update_smccc_conduit(struct alt_instr *alt, __le32 *origptr, __le32 *updptr, int nr_inst) @@ -278,44 +310,83 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, int scope) { struct arm_smccc_res res; - bool supported = true; + bool required = true; + s32 val; WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible()); - if (psci_ops.smccc_version == SMCCC_VERSION_1_0) + if (psci_ops.smccc_version == SMCCC_VERSION_1_0) { + ssbd_state = ARM64_SSBD_UNKNOWN; return false; + } - /* - * The probe function return value is either negative - * (unsupported or mitigated), positive (unaffected), or zero - * (requires mitigation). We only need to do anything in the - * last case. - */ switch (psci_ops.conduit) { case PSCI_CONDUIT_HVC: arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_ARCH_WORKAROUND_2, &res); - if ((int)res.a0 != 0) - supported = false; break; case PSCI_CONDUIT_SMC: arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_ARCH_WORKAROUND_2, &res); - if ((int)res.a0 != 0) - supported = false; break; default: - supported = false; + ssbd_state = ARM64_SSBD_UNKNOWN; + return false; } - if (supported) { - __this_cpu_write(arm64_ssbd_callback_required, 1); + val = (s32)res.a0; + + switch (val) { + case SMCCC_RET_NOT_SUPPORTED: + ssbd_state = ARM64_SSBD_UNKNOWN; + return false; + + case SMCCC_RET_NOT_REQUIRED: + pr_info_once("%s mitigation not required\n", entry->desc); + ssbd_state = ARM64_SSBD_MITIGATED; + return false; + + case SMCCC_RET_SUCCESS: + required = true; + break; + + case 1: /* Mitigation not required on this CPU */ + required = false; + break; + + default: + WARN_ON(1); + return false; + } + + switch (ssbd_state) { + case ARM64_SSBD_FORCE_DISABLE: + pr_info_once("%s disabled from command-line\n", entry->desc); + arm64_set_ssbd_mitigation(false); + required = false; + break; + + case ARM64_SSBD_KERNEL: + if (required) { + __this_cpu_write(arm64_ssbd_callback_required, 1); + arm64_set_ssbd_mitigation(true); + } + break; + + case ARM64_SSBD_FORCE_ENABLE: + pr_info_once("%s forced from command-line\n", entry->desc); arm64_set_ssbd_mitigation(true); + required = true; + break; + + default: + WARN_ON(1); + break; } - return supported; + return required; } #endif /* CONFIG_ARM64_SSBD */ -- cgit v1.2.3-59-g8ed1b