arm64: Relax ARM_SMCCC_ARCH_WORKAROUND_1 discovery

A recent update to the ARM SMCCC ARCH_WORKAROUND_1 specification
allows firmware to return a non zero, positive value to describe
that although the mitigation is implemented at the higher exception
level, the CPU on which the call is made is not affected.

Let's relax the check on the return value from ARCH_WORKAROUND_1
so that we only error out if the returned value is negative.

Fixes: b092201e0020 ("arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 52f15cd896e11ad631ac3092d9709337a9629bb4..b5a28336c07712af8d10aa62f1669b8a798065d8 100644 (file)
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -178,7 +178,7 @@ static int enable_smccc_arch_workaround_1(void *data)
        case PSCI_CONDUIT_HVC:
                arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
                                  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-               if (res.a0)
+               if ((int)res.a0 < 0)
                        return 0;
                cb = call_hvc_arch_workaround_1;
                smccc_start = __smccc_workaround_1_hvc_start;
@@ -188,7 +188,7 @@ static int enable_smccc_arch_workaround_1(void *data)
        case PSCI_CONDUIT_SMC:
                arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
                                  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-               if (res.a0)
+               if ((int)res.a0 < 0)
                        return 0;
                cb = call_smc_arch_workaround_1;
                smccc_start = __smccc_workaround_1_smc_start;