[PATCH 3/7] target/arm: Enable FEAT_CSV2_2 for -cpu max

[Richard Henderson]

There is no branch prediction in TCG, therefore there is no
need to actually include the context number into the predictor.
Therefore all we need to do is add the state for SCXTNUM_ELx.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/cpu.h    | 16 +++++++++++
 target/arm/cpu64.c  |  2 +-
 target/arm/helper.c | 70 ++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index c6c6d89a69..0b89620662 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -688,6 +688,8 @@ typedef struct CPUArchState {
         ARMPACKey apdb;
         ARMPACKey apga;
     } keys;
+
+    uint64_t scxtnum_el[4];
 #endif
 
 #if defined(CONFIG_USER_ONLY)
@@ -1211,6 +1213,7 @@ void pmu_init(ARMCPU *cpu);
 #define SCTLR_WXN     (1U << 19)
 #define SCTLR_ST      (1U << 20) /* up to ??, RAZ in v6 */
 #define SCTLR_UWXN    (1U << 20) /* v7 onward, AArch32 only */
+#define SCTLR_TSCXT   (1U << 20) /* FEAT_CSV2_1p2, AArch64 only */
 #define SCTLR_FI      (1U << 21) /* up to v7, v8 RES0 */
 #define SCTLR_IESB    (1U << 21) /* v8.2-IESB, AArch64 only */
 #define SCTLR_U       (1U << 22) /* up to v6, RAO in v7 */
@@ -4368,6 +4371,19 @@ static inline bool isar_feature_aa64_dit(const 
ARMISARegisters *id)
     return FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, DIT) != 0;
 }
 
+static inline bool isar_feature_aa64_scxtnum(const ARMISARegisters *id)
+{
+    int key = FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, CSV2);
+    if (key >= 2) {
+        return true;      /* FEAT_CSV2_2 */
+    }
+    if (key == 1) {
+        key = FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, CSV2_FRAC);
+        return key >= 2;  /* FEAT_CSV2_1p2 */
+    }
+    return false;
+}
+
 static inline bool isar_feature_aa64_ssbs(const ARMISARegisters *id)
 {
     return FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, SSBS) != 0;
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index c1006a067c..9ff08bd995 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -805,7 +805,7 @@ static void aarch64_max_initfn(Object *obj)
     t = FIELD_DP64(t, ID_AA64PFR0, SVE, 1);
     t = FIELD_DP64(t, ID_AA64PFR0, SEL2, 1);      /* FEAT_SEL2 */
     t = FIELD_DP64(t, ID_AA64PFR0, DIT, 1);       /* FEAT_DIT */
-    t = FIELD_DP64(t, ID_AA64PFR0, CSV2, 1);      /* FEAT_CSV2 */
+    t = FIELD_DP64(t, ID_AA64PFR0, CSV2, 2);      /* FEAT_CSV2_2 */
     cpu->isar.id_aa64pfr0 = t;
 
     t = cpu->isar.id_aa64pfr1;
diff --git a/target/arm/helper.c b/target/arm/helper.c
index bd1c8e01cb..66af3397ee 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1780,6 +1780,9 @@ static void scr_write(CPUARMState *env, const 
ARMCPRegInfo *ri, uint64_t value)
         if (cpu_isar_feature(aa64_mte, cpu)) {
             valid_mask |= SCR_ATA;
         }
+        if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+            valid_mask |= SCR_ENSCXT;
+        }
     } else {
         valid_mask &= ~(SCR_RW | SCR_ST);
         if (cpu_isar_feature(aa32_ras, cpu)) {
@@ -5312,6 +5315,9 @@ static void do_hcr_write(CPUARMState *env, uint64_t 
value, uint64_t valid_mask)
         if (cpu_isar_feature(aa64_mte, cpu)) {
             valid_mask |= HCR_ATA | HCR_DCT | HCR_TID5;
         }
+        if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+            valid_mask |= HCR_ENSCXT;
+        }
     }
 
     /* Clear RES0 bits.  */
@@ -5965,6 +5971,10 @@ static void define_arm_vh_e2h_redirects_aliases(ARMCPU 
*cpu)
         { K(3, 0,  5, 6, 0), K(3, 4,  5, 6, 0), K(3, 5, 5, 6, 0),
           "TFSR_EL1", "TFSR_EL2", "TFSR_EL12", isar_feature_aa64_mte },
 
+        { K(3, 0, 0xd, 0, 7), K(3, 4, 0xd, 0, 7), K(3, 5, 0xd, 0, 7),
+          "SCXTNUM_EL1", "SCXTNUM_EL2", "SCXTNUM_EL12",
+          isar_feature_aa64_scxtnum },
+
         /* TODO: ARMv8.2-SPE -- PMSCR_EL2 */
         /* TODO: ARMv8.4-Trace -- TRFCR_EL2 */
     };
@@ -7434,7 +7444,61 @@ static const ARMCPRegInfo mte_el0_cacheop_reginfo[] = {
     REGINFO_SENTINEL
 };
 
-#endif
+static CPAccessResult access_scxtnum(CPUARMState *env, const ARMCPRegInfo *ri,
+                                     bool isread)
+{
+    uint64_t hcr;
+
+    switch (arm_current_el(env)) {
+    case 0:
+        hcr = arm_hcr_el2_eff(env);
+        if ((hcr & (HCR_TGE | HCR_E2H)) != (HCR_TGE | HCR_E2H)) {
+            if (env->cp15.sctlr_el[1] & SCTLR_TSCXT) {
+                if (hcr & HCR_TGE) {
+                    return CP_ACCESS_TRAP_EL2;
+                }
+                return CP_ACCESS_TRAP;
+            }
+            if (arm_is_el2_enabled(env) && !(hcr & HCR_ENSCXT)) {
+                return CP_ACCESS_TRAP_EL2;
+            }
+        } else {
+            QEMU_FALLTHROUGH;
+    case 1:
+            if (env->cp15.sctlr_el[2] & SCTLR_TSCXT) {
+                return CP_ACCESS_TRAP_EL2;
+            }
+        }
+        QEMU_FALLTHROUGH;
+    case 2:
+        if (arm_feature(env, ARM_FEATURE_EL3)
+            && !(env->cp15.scr_el3 & SCR_ENSCXT)) {
+            return CP_ACCESS_TRAP_EL3;
+        }
+    }
+    return CP_ACCESS_OK;
+}
+
+static const ARMCPRegInfo scxtnum_reginfo[] = {
+    { .name = "SCXTNUM_EL0", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 3, .crn = 0xd, .crm = 0, .opc2 = 7,
+      .access = PL0_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[0]) },
+    { .name = "SCXTNUM_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 0xd, .crm = 0, .opc2 = 7,
+      .access = PL1_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[1]) },
+    { .name = "SCXTNUM_EL2", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 4, .crn = 0xd, .crm = 0, .opc2 = 7,
+      .access = PL2_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[2]) },
+    { .name = "SCXTNUM_EL3", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 6, .crn = 0xd, .crm = 0, .opc2 = 7,
+      .access = PL3_RW,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[3]) },
+    REGINFO_SENTINEL
+};
+#endif /* TARGET_AARCH64 */
 
 static CPAccessResult access_predinv(CPUARMState *env, const ARMCPRegInfo *ri,
                                      bool isread)
@@ -8634,6 +8698,10 @@ void register_cp_regs_for_features(ARMCPU *cpu)
         define_arm_cp_regs(cpu, mte_tco_ro_reginfo);
         define_arm_cp_regs(cpu, mte_el0_cacheop_reginfo);
     }
+
+    if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+        define_arm_cp_regs(cpu, scxtnum_reginfo);
+    }
 #endif
 
     if (cpu_isar_feature(any_predinv, cpu)) {
-- 
2.25.1