diff --git a/qemu/target/arm/cpu.h b/qemu/target/arm/cpu.h
index 809f03ec..09057938 100644
--- a/qemu/target/arm/cpu.h
+++ b/qemu/target/arm/cpu.h
@@ -477,6 +477,9 @@ typedef struct CPUARMState {
         uint64_t pmccfiltr_el0; /* Performance Monitor Filter Register */
         uint64_t vpidr_el2; /* Virtualization Processor ID Register */
         uint64_t vmpidr_el2; /* Virtualization Multiprocessor ID Register */
+        uint64_t tfsr_el[4]; /* tfsre0_el1 is index 0.  */
+        uint64_t gcr_el1;
+        uint64_t rgsr_el1;
     } cp15;
 
     struct {
@@ -1154,6 +1157,7 @@ void pmu_init(ARMCPU *cpu);
 #define PSTATE_SS (1U << 21)
 #define PSTATE_PAN (1U << 22)
 #define PSTATE_UAO (1U << 23)
+#define PSTATE_TCO (1U << 25)
 #define PSTATE_V (1U << 28)
 #define PSTATE_C (1U << 29)
 #define PSTATE_Z (1U << 30)
diff --git a/qemu/target/arm/helper.c b/qemu/target/arm/helper.c
index 39055cdd..1b348930 100644
--- a/qemu/target/arm/helper.c
+++ b/qemu/target/arm/helper.c
@@ -1717,6 +1717,9 @@ static void scr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
         if (cpu_isar_feature(aa64_pauth, cpu)) {
             valid_mask |= SCR_API | SCR_APK;
         }
+        if (cpu_isar_feature(aa64_mte, cpu)) {
+            valid_mask |= SCR_ATA;
+        }
     } else {
         valid_mask &= ~(SCR_RW | SCR_ST);
     }
@@ -4957,17 +4960,22 @@ static void do_hcr_write(CPUARMState *env, uint64_t value, uint64_t valid_mask)
         if (cpu_isar_feature(aa64_pauth, cpu)) {
             valid_mask |= HCR_API | HCR_APK;
         }
+        if (cpu_isar_feature(aa64_mte, cpu)) {
+            valid_mask |= HCR_ATA | HCR_DCT | HCR_TID5;
+        }
     }
 
     /* Clear RES0 bits.  */
     value &= valid_mask;
 
-    /* These bits change the MMU setup:
+    /*
+     * These bits change the MMU setup:
      * HCR_VM enables stage 2 translation
      * HCR_PTW forbids certain page-table setups
-     * HCR_DC Disables stage1 and enables stage2 translation
+     * HCR_DC disables stage1 and enables stage2 translation
+     * HCR_DCT enables tagging on (disabled) stage1 translation
      */
-    if ((env->cp15.hcr_el2 ^ value) & (HCR_VM | HCR_PTW | HCR_DC)) {
+    if ((env->cp15.hcr_el2 ^ value) & (HCR_VM | HCR_PTW | HCR_DC | HCR_DCT)) {
         tlb_flush(CPU(cpu));
     }
     env->cp15.hcr_el2 = value;
@@ -5583,6 +5591,9 @@ static void define_arm_vh_e2h_redirects_aliases(ARMCPU *cpu)
         { K(3, 0,  1, 2, 0), K(3, 4,  1, 2, 0), K(3, 5, 1, 2, 0),
           "ZCR_EL1", "ZCR_EL2", "ZCR_EL12", isar_feature_aa64_sve },
 
+        { 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 },
+
         /* TODO: ARMv8.2-SPE -- PMSCR_EL2 */
         /* TODO: ARMv8.4-Trace -- TRFCR_EL2 */
     };
@@ -6549,6 +6560,87 @@ static const ARMCPRegInfo dcpodp_reg[] = {
 };
 #endif /*CONFIG_USER_ONLY*/
 
+static CPAccessResult access_aa64_tid5(CPUARMState *env, const ARMCPRegInfo *ri,
+                                       bool isread)
+{
+    if ((arm_current_el(env) < 2) && (arm_hcr_el2_eff(env) & HCR_TID5)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+
+    return CP_ACCESS_OK;
+}
+
+static CPAccessResult access_mte(CPUARMState *env, const ARMCPRegInfo *ri,
+                                 bool isread)
+{
+    int el = arm_current_el(env);
+
+    if (el < 2 &&
+        arm_feature(env, ARM_FEATURE_EL2) &&
+        !(arm_hcr_el2_eff(env) & HCR_ATA)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    if (el < 3 &&
+        arm_feature(env, ARM_FEATURE_EL3) &&
+        !(env->cp15.scr_el3 & SCR_ATA)) {
+        return CP_ACCESS_TRAP_EL3;
+    }
+    return CP_ACCESS_OK;
+}
+
+static uint64_t tco_read(CPUARMState *env, const ARMCPRegInfo *ri)
+{
+    return env->pstate & PSTATE_TCO;
+}
+
+static void tco_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t val)
+{
+    env->pstate = (env->pstate & ~PSTATE_TCO) | (val & PSTATE_TCO);
+}
+
+static const ARMCPRegInfo mte_reginfo[] = {
+    { .name = "TFSRE0_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 5, .crm = 6, .opc2 = 1,
+      .access = PL1_RW, .accessfn = access_mte,
+      .fieldoffset = offsetof(CPUARMState, cp15.tfsr_el[0]) },
+    { .name = "TFSR_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 5, .crm = 6, .opc2 = 0,
+      .access = PL1_RW, .accessfn = access_mte,
+      .fieldoffset = offsetof(CPUARMState, cp15.tfsr_el[1]) },
+    { .name = "TFSR_EL2", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 4, .crn = 5, .crm = 6, .opc2 = 0,
+      .access = PL2_RW, .accessfn = access_mte,
+      .fieldoffset = offsetof(CPUARMState, cp15.tfsr_el[2]) },
+    { .name = "TFSR_EL3", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 6, .crn = 5, .crm = 6, .opc2 = 0,
+      .access = PL3_RW,
+      .fieldoffset = offsetof(CPUARMState, cp15.tfsr_el[3]) },
+    { .name = "RGSR_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 1, .crm = 0, .opc2 = 5,
+      .access = PL1_RW, .accessfn = access_mte,
+      .fieldoffset = offsetof(CPUARMState, cp15.rgsr_el1) },
+    { .name = "GCR_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 1, .crm = 0, .opc2 = 6,
+      .access = PL1_RW, .accessfn = access_mte,
+      .fieldoffset = offsetof(CPUARMState, cp15.gcr_el1) },
+    { .name = "GMID_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 1, .crn = 0, .crm = 0, .opc2 = 4,
+      .access = PL1_R, .accessfn = access_aa64_tid5,
+      .type = ARM_CP_CONST, .resetvalue = GMID_EL1_BS },
+    { .name = "TCO", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 3, .crn = 4, .crm = 2, .opc2 = 7,
+      .type = ARM_CP_NO_RAW,
+      .access = PL0_RW, .readfn = tco_read, .writefn = tco_write },
+    REGINFO_SENTINEL
+};
+
+static const ARMCPRegInfo mte_tco_ro_reginfo[] = {
+    { .name = "TCO", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 3, .crn = 4, .crm = 2, .opc2 = 7,
+      .type = ARM_CP_CONST, .access = PL0_RW, },
+    REGINFO_SENTINEL
+};
+
 #endif
 
 static CPAccessResult access_predinv(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -7660,6 +7752,17 @@ void register_cp_regs_for_features(ARMCPU *cpu)
         }
     }
 #endif /*CONFIG_USER_ONLY*/
+
+    /*
+     * If full MTE is enabled, add all of the system registers.
+     * If only "instructions available at EL0" are enabled,
+     * then define only a RAZ/WI version of PSTATE.TCO.
+     */
+    if (cpu_isar_feature(aa64_mte, cpu)) {
+        define_arm_cp_regs(cpu, mte_reginfo);
+    } else if (cpu_isar_feature(aa64_mte_insn_reg, cpu)) {
+        define_arm_cp_regs(cpu, mte_tco_ro_reginfo);
+    }
 #endif
 
     if (cpu_isar_feature(any_predinv, cpu)) {
diff --git a/qemu/target/arm/internals.h b/qemu/target/arm/internals.h
index 15897fca..9e7e93a3 100644
--- a/qemu/target/arm/internals.h
+++ b/qemu/target/arm/internals.h
@@ -1165,6 +1165,9 @@ static inline uint32_t aarch64_pstate_valid_mask(const ARMISARegisters *id)
     if (isar_feature_aa64_uao(id)) {
         valid |= PSTATE_UAO;
     }
+    if (isar_feature_aa64_mte(id)) {
+        valid |= PSTATE_TCO;
+    }
 
     return valid;
 }
@@ -1238,4 +1241,10 @@ bool get_phys_addr(CPUARMState *env, target_ulong address,
 
 #endif /* !CONFIG_USER_ONLY */
 
+/*
+ * The log2 of the words in the tag block, for GMID_EL1.BS.
+ * The is the maximum, 256 bytes, which manipulates 64-bits of tags.
+ */
+#define GMID_EL1_BS  6
+
 #endif
diff --git a/qemu/target/arm/translate-a64.c b/qemu/target/arm/translate-a64.c
index 903809b0..4da61e2c 100644
--- a/qemu/target/arm/translate-a64.c
+++ b/qemu/target/arm/translate-a64.c
@@ -1805,6 +1805,27 @@ static void handle_msr_i(DisasContext *s, uint32_t insn,
         s->base.is_jmp = DISAS_UPDATE_EXIT;
         break;
 
+    case 0x1c: /* TCO */
+        if (dc_isar_feature(aa64_mte, s)) {
+            /* Full MTE is enabled -- set the TCO bit as directed. */
+            if (crm & 1) {
+                set_pstate_bits(s, PSTATE_TCO);
+            } else {
+                clear_pstate_bits(s, PSTATE_TCO);
+            }
+            t1 = tcg_const_i32(tcg_ctx, s->current_el);
+            //gen_helper_rebuild_hflags_a64(tcg_ctx, tcg_ctx->cpu_env, t1);
+            tcg_temp_free_i32(tcg_ctx, t1);
+            /* Many factors, including TCO, go into MTE_ACTIVE. */
+            s->base.is_jmp = DISAS_UPDATE_NOCHAIN;
+        } else if (dc_isar_feature(aa64_mte_insn_reg, s)) {
+            /* Only "instructions accessible at EL0" -- PSTATE.TCO is WI.  */
+            s->base.is_jmp = DISAS_NEXT;
+        } else {
+            goto do_unallocated;
+        }
+        break;
+
     default:
     do_unallocated:
         unallocated_encoding(s);