4.9-stable review patch. If anyone has any objections, please let me know.
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From: Marc Zyngier marc.zyngier@arm.com
commit a725e3dda1813ed306734823ac4c65ca04e38500 upstream.
As for Spectre variant-2, we rely on SMCCC 1.1 to provide the discovery mechanism for detecting the SSBD mitigation.
A new capability is also allocated for that purpose, and a config option.
Reviewed-by: Julien Grall julien.grall@arm.com Reviewed-by: Mark Rutland mark.rutland@arm.com Acked-by: Will Deacon will.deacon@arm.com Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/Kconfig | 9 +++++ arch/arm64/include/asm/cpucaps.h | 3 + arch/arm64/kernel/cpu_errata.c | 69 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 80 insertions(+), 1 deletion(-)
--- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -776,6 +776,15 @@ config HARDEN_BRANCH_PREDICTOR
If unsure, say Y.
+config ARM64_SSBD + bool "Speculative Store Bypass Disable" if EXPERT + default y + help + This enables mitigation of the bypassing of previous stores + by speculative loads. + + If unsure, say Y. + menuconfig ARMV8_DEPRECATED bool "Emulate deprecated/obsolete ARMv8 instructions" depends on COMPAT --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -36,7 +36,8 @@ #define ARM64_MISMATCHED_CACHE_LINE_SIZE 15 #define ARM64_UNMAP_KERNEL_AT_EL0 16 #define ARM64_HARDEN_BRANCH_PREDICTOR 17 +#define ARM64_SSBD 18
-#define ARM64_NCAPS 18 +#define ARM64_NCAPS 19
#endif /* __ASM_CPUCAPS_H */ --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -211,6 +211,67 @@ void __init arm64_update_smccc_conduit(s
*updptr = cpu_to_le32(insn); } + +static void arm64_set_ssbd_mitigation(bool state) +{ + switch (psci_ops.conduit) { + case PSCI_CONDUIT_HVC: + arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_2, state, NULL); + break; + + case PSCI_CONDUIT_SMC: + arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2, state, NULL); + break; + + default: + WARN_ON_ONCE(1); + break; + } +} + +static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, + int scope) +{ + struct arm_smccc_res res; + bool supported = true; + + WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible()); + + if (psci_ops.smccc_version == SMCCC_VERSION_1_0) + 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; + } + + if (supported) { + __this_cpu_write(arm64_ssbd_callback_required, 1); + arm64_set_ssbd_mitigation(true); + } + + return supported; +} #endif /* CONFIG_ARM64_SSBD */
#define MIDR_RANGE(model, min, max) \ @@ -336,6 +397,14 @@ const struct arm64_cpu_capabilities arm6 .enable = enable_smccc_arch_workaround_1, }, #endif +#ifdef CONFIG_ARM64_SSBD + { + .desc = "Speculative Store Bypass Disable", + .def_scope = SCOPE_LOCAL_CPU, + .capability = ARM64_SSBD, + .matches = has_ssbd_mitigation, + }, +#endif { } };