arm64: mte: CPU feature detection for Asymm MTE

Add the cpufeature entries to detect the presence of Asymmetric MTE.

Note: The tag checking mode is initialized via cpu_enable_mte() ->
kasan_init_hw_tags() hence to enable it we require asymmetric mode
to be at least on the boot CPU. If the boot CPU does not have it, it is
fine for late CPUs to have it as long as the feature is not enabled
(ARM64_CPUCAP_BOOT_CPU_FEATURE).

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20211006154751.4463-4-vincenzo.frascino@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6ec7036..9e3e8ad 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2321,6 +2321,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
                .sign = FTR_UNSIGNED,
                .cpu_enable = cpu_enable_mte,
        },
+       {
+               .desc = "Asymmetric MTE Tag Check Fault",
+               .capability = ARM64_MTE_ASYMM,
+               .type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
+               .matches = has_cpuid_feature,
+               .sys_reg = SYS_ID_AA64PFR1_EL1,
+               .field_pos = ID_AA64PFR1_MTE_SHIFT,
+               .min_field_value = ID_AA64PFR1_MTE_ASYMM,
+               .sign = FTR_UNSIGNED,
+       },
 #endif /* CONFIG_ARM64_MTE */
        {
                .desc = "RCpc load-acquire (LDAPR)",

diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 49305c2..74a569b 100644 (file)
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -39,6 +39,7 @@ HW_DBM
 KVM_PROTECTED_MODE
 MISMATCHED_CACHE_TYPE
 MTE
+MTE_ASYMM
 SPECTRE_V2
 SPECTRE_V3A
 SPECTRE_V4