[PATCH v2 06/13] arm64: cpufeature: Detect E2H0 not being implemented

[Marc Zyngier]

FEAT_E2H0 is a new feature that indicates whether or not HCR_EL2.E2H
can be set to 0. Amusingly, this feature is set to 0 when implemented,
and otherwise negative.

Add a new capability and detection infrastructure to detect the
absence of FEAT_E2H0.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kernel/cpufeature.c | 7 +++++++
 arch/arm64/tools/cpucaps       | 1 +
 2 files changed, 8 insertions(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 41db7f993eef..e0d64e8b4851 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2787,6 +2787,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, EVT, IMP)
 	},
+	{
+		.desc = "FEAT_E2H0 not implemented",
+		.capability = ARM64_HCR_E2H_RES1,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		ARM64_CPUID_FIELDS_NEG(ID_AA64MMFR4_EL1, E2H0, NI)
+	},
 	{},
 };
 
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index b98c38288a9d..8866ea9bf995 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -52,6 +52,7 @@ HAS_TIDCP1
 HAS_TLB_RANGE
 HAS_VIRT_HOST_EXTN
 HAS_WFXT
+HCR_E2H_RES1
 HW_DBM
 KVM_HVHE
 KVM_PROTECTED_MODE
-- 
2.39.2