target/arm: Allow relevant HCR bits to be written for FEAT_EVT

FEAT_EVT adds five new bits to the HCR_EL2 register: TTLBIS, TTLBOS,
TICAB, TOCU and TID4.  These allow the guest to enable trapping of
various EL1 instructions to EL2.  In this commit, add the necessary
code to allow the guest to set these bits if the feature is present;
because the bit is always zero when the feature isn't present we
won't need to use explicit feature checks in the "trap on condition"
tests in the following commits.

Note that although full implementation of the feature (mandatory from
Armv8.5 onward) requires all five trap bits, the ID registers permit
a value indicating that only TICAB, TOCU and TID4 are implemented,
which might be the case for CPUs between Armv8.2 and Armv8.5.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

target/arm/cpu.h

@@ -3757,6 +3757,16 @@ static inline bool isar_feature_aa32_tts2uxn(const ARMISARegisters *id)
     return FIELD_EX32(id->id_mmfr4, ID_MMFR4, XNX) != 0;
 }
 
+static inline bool isar_feature_aa32_half_evt(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_mmfr4, ID_MMFR4, EVT) >= 1;
+}
+
+static inline bool isar_feature_aa32_evt(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_mmfr4, ID_MMFR4, EVT) >= 2;
+}
+
 static inline bool isar_feature_aa32_dit(const ARMISARegisters *id)
 {
     return FIELD_EX32(id->id_pfr0, ID_PFR0, DIT) != 0;
@@ -4029,6 +4039,16 @@ static inline bool isar_feature_aa64_ids(const ARMISARegisters *id)
     return FIELD_EX64(id->id_aa64mmfr2, ID_AA64MMFR2, IDS) != 0;
 }
 
+static inline bool isar_feature_aa64_half_evt(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->id_aa64mmfr2, ID_AA64MMFR2, EVT) >= 1;
+}
+
+static inline bool isar_feature_aa64_evt(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->id_aa64mmfr2, ID_AA64MMFR2, EVT) >= 2;
+}
+
 static inline bool isar_feature_aa64_bti(const ARMISARegisters *id)
 {
     return FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, BT) != 0;
@@ -4313,6 +4333,16 @@ static inline bool isar_feature_any_ras(const ARMISARegisters *id)
     return isar_feature_aa64_ras(id) || isar_feature_aa32_ras(id);
 }
 
+static inline bool isar_feature_any_half_evt(const ARMISARegisters *id)
+{
+    return isar_feature_aa64_half_evt(id) || isar_feature_aa32_half_evt(id);
+}
+
+static inline bool isar_feature_any_evt(const ARMISARegisters *id)
+{
+    return isar_feature_aa64_evt(id) || isar_feature_aa32_evt(id);
+}
+
 /*
  * Forward to the above feature tests given an ARMCPU pointer.
  */

target/arm/helper.c

@@ -5267,6 +5267,12 @@ static void do_hcr_write(CPUARMState *env, uint64_t value, uint64_t valid_mask)
         }
     }
 
+    if (cpu_isar_feature(any_evt, cpu)) {
+        valid_mask |= HCR_TTLBIS | HCR_TTLBOS | HCR_TICAB | HCR_TOCU | HCR_TID4;
+    } else if (cpu_isar_feature(any_half_evt, cpu)) {
+        valid_mask |= HCR_TICAB | HCR_TOCU | HCR_TID4;
+    }
+
     /* Clear RES0 bits.  */
     value &= valid_mask;