[PATCH v3 04/17] arm64: Add KVM_HVHE capability and has_hvhe() predicate

[Marc Zyngier <maz@xxxxxxxxxx>]

Expose a capability keying the hVHE feature as well as a new
predicate testing it. Nothing is so far using it, and nothing
is enabling it yet.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
 arch/arm64/include/asm/cpufeature.h |  1 +
 arch/arm64/include/asm/virt.h       |  8 ++++++++
 arch/arm64/kernel/cpufeature.c      | 19 +++++++++++++++++++
 arch/arm64/tools/cpucaps            |  1 +
 4 files changed, 29 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index bc1009890180..3d4b547ae312 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -16,6 +16,7 @@
 #define cpu_feature(x)		KERNEL_HWCAP_ ## x
 
 #define ARM64_SW_FEATURE_OVERRIDE_NOKASLR	0
+#define ARM64_SW_FEATURE_OVERRIDE_HVHE		4
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 21e94068804d..5227db7640c8 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -142,6 +142,14 @@ static __always_inline bool is_protected_kvm_enabled(void)
 		return cpus_have_final_cap(ARM64_KVM_PROTECTED_MODE);
 }
 
+static __always_inline bool has_hvhe(void)
+{
+	if (is_vhe_hyp_code())
+		return false;
+
+	return cpus_have_final_cap(ARM64_KVM_HVHE);
+}
+
 static inline bool is_hyp_nvhe(void)
 {
 	return is_hyp_mode_available() && !is_kernel_in_hyp_mode();
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2d2b7bb5fa0c..c743b1a5ae31 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1998,6 +1998,19 @@ static bool has_nested_virt_support(const struct arm64_cpu_capabilities *cap,
 	return true;
 }
 
+static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
+			  int __unused)
+{
+	u64 val;
+
+	val = read_sysreg(id_aa64mmfr1_el1);
+	if (!cpuid_feature_extract_unsigned_field(val, ID_AA64MMFR1_EL1_VH_SHIFT))
+		return false;
+
+	val = arm64_sw_feature_override.val & arm64_sw_feature_override.mask;
+	return cpuid_feature_extract_unsigned_field(val, ARM64_SW_FEATURE_OVERRIDE_HVHE);
+}
+
 #ifdef CONFIG_ARM64_PAN
 static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
 {
@@ -2643,6 +2656,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_dit,
 		ARM64_CPUID_FIELDS(ID_AA64PFR0_EL1, DIT, IMP)
 	},
+	{
+		.desc = "VHE for hypervisor only",
+		.capability = ARM64_KVM_HVHE,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = hvhe_possible,
+	},
 	{},
 };
 
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 40ba95472594..3c23a55d7c2f 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -47,6 +47,7 @@ HAS_TLB_RANGE
 HAS_VIRT_HOST_EXTN
 HAS_WFXT
 HW_DBM
+KVM_HVHE
 KVM_PROTECTED_MODE
 MISMATCHED_CACHE_TYPE
 MTE
-- 
2.34.1