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-rw-r--r--target/arm/cpu.h6
-rw-r--r--target/arm/helper.c30
2 files changed, 28 insertions, 8 deletions
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index bc7a69a875..266c1a9ea1 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1315,6 +1315,7 @@ void pmu_init(ARMCPU *cpu);
 #define SCTLR_EnIB    (1U << 30) /* v8.3, AArch64 only */
 #define SCTLR_EnIA    (1U << 31) /* v8.3, AArch64 only */
 #define SCTLR_DSSBS_32 (1U << 31) /* v8.5, AArch32 only */
+#define SCTLR_MSCEN   (1ULL << 33) /* FEAT_MOPS */
 #define SCTLR_BT0     (1ULL << 35) /* v8.5-BTI */
 #define SCTLR_BT1     (1ULL << 36) /* v8.5-BTI */
 #define SCTLR_ITFSB   (1ULL << 37) /* v8.5-MemTag */
@@ -4281,6 +4282,11 @@ static inline bool isar_feature_aa64_doublelock(const ARMISARegisters *id)
     return FIELD_SEX64(id->id_aa64dfr0, ID_AA64DFR0, DOUBLELOCK) >= 0;
 }
 
+static inline bool isar_feature_aa64_mops(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->id_aa64isar2, ID_AA64ISAR2, MOPS);
+}
+
 /*
  * Feature tests for "does this exist in either 32-bit or 64-bit?"
  */
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 594985d7c8..83620787b4 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -5980,7 +5980,10 @@ static void hcrx_write(CPUARMState *env, const ARMCPRegInfo *ri,
 {
     uint64_t valid_mask = 0;
 
-    /* No features adding bits to HCRX are implemented. */
+    /* FEAT_MOPS adds MSCEn and MCE2 */
+    if (cpu_isar_feature(aa64_mops, env_archcpu(env))) {
+        valid_mask |= HCRX_MSCEN | HCRX_MCE2;
+    }
 
     /* Clear RES0 bits.  */
     env->cp15.hcrx_el2 = value & valid_mask;
@@ -6009,13 +6012,24 @@ uint64_t arm_hcrx_el2_eff(CPUARMState *env)
 {
     /*
      * The bits in this register behave as 0 for all purposes other than
-     * direct reads of the register if:
-     *   - EL2 is not enabled in the current security state,
-     *   - SCR_EL3.HXEn is 0.
-     */
-    if (!arm_is_el2_enabled(env)
-        || (arm_feature(env, ARM_FEATURE_EL3)
-            && !(env->cp15.scr_el3 & SCR_HXEN))) {
+     * direct reads of the register if SCR_EL3.HXEn is 0.
+     * If EL2 is not enabled in the current security state, then the
+     * bit may behave as if 0, or as if 1, depending on the bit.
+     * For the moment, we treat the EL2-disabled case as taking
+     * priority over the HXEn-disabled case. This is true for the only
+     * bit for a feature which we implement where the answer is different
+     * for the two cases (MSCEn for FEAT_MOPS).
+     * This may need to be revisited for future bits.
+     */
+    if (!arm_is_el2_enabled(env)) {
+        uint64_t hcrx = 0;
+        if (cpu_isar_feature(aa64_mops, env_archcpu(env))) {
+            /* MSCEn behaves as 1 if EL2 is not enabled */
+            hcrx |= HCRX_MSCEN;
+        }
+        return hcrx;
+    }
+    if (arm_feature(env, ARM_FEATURE_EL3) && !(env->cp15.scr_el3 & SCR_HXEN)) {
         return 0;
     }
     return env->cp15.hcrx_el2;