Commit af33d746 authored Apr 15, 2019 by Marc Zyngier Committed by Greg Kroah-Hartman Oct 11, 2019

arm64: Use firmware to detect CPUs that are not affected by Spectre-v2



commit 517953c2c47f9c00a002f588ac856a5bc70cede3 upstream.

The SMCCC ARCH_WORKAROUND_1 service can indicate that although the
firmware knows about the Spectre-v2 mitigation, this particular
CPU is not vulnerable, and it is thus not necessary to call
the firmware on this CPU.

Let's use this information to our benefit.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 17d1acc4

arch/arm64/kernel/cpu_errata.c

+23 −9

Original line number	Diff line number	Diff line
		@@ -198,23 +198,37 @@ static int detect_harden_bp_fw(void)
		case PSCI_CONDUIT_HVC:
		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
		ARM_SMCCC_ARCH_WORKAROUND_1, &res);
		if ((int)res.a0 < 0)
		return -1;
		switch ((int)res.a0) {
		case 1:
		/* Firmware says we're just fine */
		return 0;
		case 0:
		cb = call_hvc_arch_workaround_1;
		/* This is a guest, no need to patch KVM vectors */
		smccc_start = NULL;
		smccc_end = NULL;
		break;
		default:
		return -1;
		}
		break;

		case PSCI_CONDUIT_SMC:
		arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
		ARM_SMCCC_ARCH_WORKAROUND_1, &res);
		if ((int)res.a0 < 0)
		return -1;
		switch ((int)res.a0) {
		case 1:
		/* Firmware says we're just fine */
		return 0;
		case 0:
		cb = call_smc_arch_workaround_1;
		smccc_start = __smccc_workaround_1_smc_start;
		smccc_end = __smccc_workaround_1_smc_end;
		break;
		default:
		return -1;
		}
		break;

		default:
		return -1;