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Commit e7037bd9 authored by Marc Zyngier's avatar Marc Zyngier Committed by Greg Kroah-Hartman
Browse files

arm64: Add ARCH_WORKAROUND_2 probing 



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: default avatarJulien Grall <julien.grall@arm.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d8174bd7

arch/arm64/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/include/asm/cpucaps.h

+2 −1
Original line number Diff line number Diff line
@@ -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 */

arch/arm64/kernel/cpu_errata.c

+69 −0
Original line number Diff line number Diff line
@@ -211,6 +211,67 @@ 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 MIDR_RANGE(model, min, max) \
@@ -335,6 +396,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = { 
		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),

		.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

	{

	}