[RFC PATCH 4/5] target/arm: enable feature ARM_FEATURE_EL2 if EL2 is supported

[Miguel Luis <miguel.luis@oracle.com>]

From: Haibo Xu <haibo.xu@linaro.org>

KVM_CAP_ARM_EL2 must be supported by the cpu to enable ARM_FEATURE_EL2.
EL2 bits on ID_AA64PFR0 state unsupported on the value 0b0000.

Ref: https://lore.kernel.org/qemu-devel/b7c2626e6c720ccc43e57197dff3dac72d613640.1616052890.git.haibo.xu@linaro.org/

Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
[Miguel Luis: use of ID_AA64PFR0 for cpu features]
Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
---
 target/arm/cpu.h   |  2 +-
 target/arm/kvm64.c | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 9aeed3c848..de2a88b43e 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -3961,7 +3961,7 @@ static inline bool isar_feature_aa64_aa32_el1(const ARMISARegisters *id)
 
 static inline bool isar_feature_aa64_aa32_el2(const ARMISARegisters *id)
 {
-    return FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, EL2) >= 2;
+    return FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, EL2) != 0;
 }
 
 static inline bool isar_feature_aa64_ras(const ARMISARegisters *id)
diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
index be8144a2b5..f7ebd731aa 100644
--- a/target/arm/kvm64.c
+++ b/target/arm/kvm64.c
@@ -505,6 +505,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
      */
     int fdarray[3];
     bool sve_supported;
+    bool el2_supported;
     bool pmu_supported = false;
     uint64_t features = 0;
     int err;
@@ -535,6 +536,14 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         init.features[0] |= 1 << KVM_ARM_VCPU_SVE;
     }
 
+    /*
+     * Ask for EL2 if supported.
+     */
+    el2_supported = kvm_arm_el2_supported();
+    if (el2_supported) {
+        init.features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
+    }
+
     /*
      * Ask for Pointer Authentication if supported, so that we get
      * the unsanitized field values for AA64ISAR1_EL1.
@@ -714,6 +723,10 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     features |= 1ULL << ARM_FEATURE_PMU;
     features |= 1ULL << ARM_FEATURE_GENERIC_TIMER;
 
+    if (el2_supported) {
+        features |= 1ULL << ARM_FEATURE_EL2;
+    }
+
     ahcf->features = features;
 
     return true;
@@ -881,6 +894,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
         assert(kvm_arm_sve_supported());
         cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_SVE;
     }
+    if (cpu_isar_feature(aa64_aa32_el2, cpu)) {
+        cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
+    }
     if (cpu_isar_feature(aa64_pauth, cpu)) {
         cpu->kvm_init_features[0] |= (1 << KVM_ARM_VCPU_PTRAUTH_ADDRESS |
                                       1 << KVM_ARM_VCPU_PTRAUTH_GENERIC);
-- 
2.39.2