The ACTLR2 and HACTLR2 AArch32 system registers didn't exist in ARMv7
or the original ARMv8.  They were later added as optional registers,
whose presence is signaled by the ID_MMFR4.AC2 field.  From ARMv8.2
they are mandatory (ie ID_MMFR4.AC2 must be non-zero).

We implemented HACTLR2 in commit 0e0456ab8895a5e85, but we
incorrectly made it exist for all v8 CPUs, and we didn't implement
ACTLR2 at all.

Sort this out by implementing both registers only when they are
supposed to exist, and setting the ID_MMFR4 bit for -cpu max.

Note that this removes HACTLR2 from our Cortex-A53, -A47 and -A72
CPU models; this is correct, because those CPUs do not implement
this register.

Fixes: 0e0456ab8895a5e85
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
 target/arm/cpu.h    |  5 +++++
 target/arm/cpu.c    |  1 +
 target/arm/cpu64.c  |  4 ++++
 target/arm/helper.c | 32 +++++++++++++++++++++++---------
 4 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index c6af3290caf..b4c83a1cb52 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -3531,6 +3531,11 @@ static inline bool isar_feature_aa32_hpd(const 
ARMISARegisters *id)
     return FIELD_EX32(id->id_mmfr4, ID_MMFR4, HPDS) != 0;
 }
 
+static inline bool isar_feature_aa32_ac2(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_mmfr4, ID_MMFR4, AC2) != 0;
+}
+
 /*
  * 64-bit feature tests via id registers.
  */
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index c46bb5a5c09..9f618e120aa 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -2718,6 +2718,7 @@ static void arm_max_initfn(Object *obj)
 
             t = cpu->isar.id_mmfr4;
             t = FIELD_DP32(t, ID_MMFR4, HPDS, 1); /* AA32HPD */
+            t = FIELD_DP32(t, ID_MMFR4, AC2, 1); /* ACTLR2, HACTLR2 */
             cpu->isar.id_mmfr4 = t;
         }
 #endif
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 8430d432943..32cf8ee98b0 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -703,6 +703,10 @@ static void aarch64_max_initfn(Object *obj)
         u = FIELD_DP32(u, ID_MMFR3, PAN, 2); /* ATS1E1 */
         cpu->isar.id_mmfr3 = u;
 
+        u = cpu->isar.id_mmfr4;
+        u = FIELD_DP32(u, ID_MMFR4, AC2, 1); /* ACTLR2, HACTLR2 implemented */
+        cpu->isar.id_mmfr4 = u;
+
         u = cpu->isar.id_aa64dfr0;
         u = FIELD_DP64(u, ID_AA64DFR0, PMUVER, 5); /* v8.4-PMU */
         cpu->isar.id_aa64dfr0 = u;
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 56b1c08f027..513f4edbb46 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6862,6 +6862,27 @@ static const ARMCPRegInfo ats1cp_reginfo[] = {
 };
 #endif
 
+/*
+ * ACTLR2 and HACTLR2 map to ACTLR_EL1[63:32] and
+ * ACTLR_EL2[63:32]. They exist only if the ID_MMFR4.AC2 field
+ * is non-zero, which is never for ARMv7, optionally in ARMv8
+ * and mandatorily for ARMv8.2 and up.
+ * ACTLR2 is banked for S and NS if EL3 is AArch32. Since QEMU's
+ * implementation is RAZ/WI we can ignore this detail, as we
+ * do for ACTLR.
+ */
+static const ARMCPRegInfo actlr2_hactlr2_reginfo[] = {
+    { .name = "ACTLR2", .state = ARM_CP_STATE_AA32,
+      .cp = 15, .opc1 = 0, .crn = 1, .crm = 0, .opc2 = 3,
+      .access = PL1_RW, .type = ARM_CP_CONST,
+      .resetvalue = 0 },
+    { .name = "HACTLR2", .state = ARM_CP_STATE_AA32,
+      .cp = 15, .opc1 = 4, .crn = 1, .crm = 0, .opc2 = 3,
+      .access = PL2_RW, .type = ARM_CP_CONST,
+      .resetvalue = 0 },
+    REGINFO_SENTINEL
+};
+
 void register_cp_regs_for_features(ARMCPU *cpu)
 {
     /* Register all the coprocessor registers based on feature bits */
@@ -7623,15 +7644,8 @@ void register_cp_regs_for_features(ARMCPU *cpu)
             REGINFO_SENTINEL
         };
         define_arm_cp_regs(cpu, auxcr_reginfo);
-        if (arm_feature(env, ARM_FEATURE_V8)) {
-            /* HACTLR2 maps to ACTLR_EL2[63:32] and is not in ARMv7 */
-            ARMCPRegInfo hactlr2_reginfo = {
-                .name = "HACTLR2", .state = ARM_CP_STATE_AA32,
-                .cp = 15, .opc1 = 4, .crn = 1, .crm = 0, .opc2 = 3,
-                .access = PL2_RW, .type = ARM_CP_CONST,
-                .resetvalue = 0
-            };
-            define_one_arm_cp_reg(cpu, &hactlr2_reginfo);
+        if (cpu_isar_feature(aa32_ac2, cpu)) {
+            define_arm_cp_regs(cpu, actlr2_hactlr2_reginfo);
         }
     }
 
-- 
2.20.1


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