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arm64: Add ARCH_WORKAROUND_2 probing

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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>
This commit is contained in:
Marc Zyngier 2018-05-29 13:11:08 +01:00 committed by Catalin Marinas
parent 5cf9ce6e5e
commit a725e3dda1
3 changed files with 80 additions and 1 deletions
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9
arch/arm64/Kconfig
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@ -940,6 +940,15 @@ config HARDEN_EL2_VECTORS
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

3
arch/arm64/include/asm/cpucaps.h
View File

@ -48,7 +48,8 @@
#define ARM64_HAS_CACHE_IDC 27
#define ARM64_HAS_CACHE_DIC 28
#define ARM64_HW_DBM 29
#define ARM64_SSBD 30
#define ARM64_NCAPS 30
#define ARM64_NCAPS 31
#endif /* __ASM_CPUCAPS_H */

69
arch/arm64/kernel/cpu_errata.c
View File

@ -256,6 +256,67 @@ void __init arm64_update_smccc_conduit(struct alt_instr *alt,
*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 CAP_MIDR_RANGE(model, v_min, r_min, v_max, r_max) \
@ -512,6 +573,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
ERRATA_MIDR_RANGE_LIST(arm64_harden_el2_vectors),
},
#endif
#ifdef CONFIG_ARM64_SSBD
{
.desc = "Speculative Store Bypass Disable",
.capability = ARM64_SSBD,
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
.matches = has_ssbd_mitigation,
},
#endif
{
}