diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 98240224c0c..0f21b6ed803 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1840,6 +1840,13 @@ FIELD(ID_DFR0, MPROFDBG, 20, 4)
 FIELD(ID_DFR0, PERFMON, 24, 4)
 FIELD(ID_DFR0, TRACEFILT, 28, 4)
 
+FIELD(DBGDIDR, SE_IMP, 12, 1)
+FIELD(DBGDIDR, NSUHD_IMP, 14, 1)
+FIELD(DBGDIDR, VERSION, 16, 4)
+FIELD(DBGDIDR, CTX_CMPS, 20, 4)
+FIELD(DBGDIDR, BRPS, 24, 4)
+FIELD(DBGDIDR, WRPS, 28, 4)
+
 FIELD(MVFR0, SIMDREG, 0, 4)
 FIELD(MVFR0, FPSP, 4, 4)
 FIELD(MVFR0, FPDP, 8, 4)
diff --git a/target/arm/internals.h b/target/arm/internals.h
index 052449b4826..39239186def 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -931,6 +931,48 @@ static inline uint32_t arm_debug_exception_fsr(CPUARMState *env)
     }
 }
 
+/**
+ * arm_num_brps: Return number of implemented breakpoints.
+ * Note that the ID register BRPS field is "number of bps - 1",
+ * and we return the actual number of breakpoints.
+ */
+static inline int arm_num_brps(ARMCPU *cpu)
+{
+    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
+        return FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, BRPS) + 1;
+    } else {
+        return FIELD_EX32(cpu->dbgdidr, DBGDIDR, BRPS) + 1;
+    }
+}
+
+/**
+ * arm_num_wrps: Return number of implemented watchpoints.
+ * Note that the ID register WRPS field is "number of wps - 1",
+ * and we return the actual number of watchpoints.
+ */
+static inline int arm_num_wrps(ARMCPU *cpu)
+{
+    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
+        return FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, WRPS) + 1;
+    } else {
+        return FIELD_EX32(cpu->dbgdidr, DBGDIDR, WRPS) + 1;
+    }
+}
+
+/**
+ * arm_num_ctx_cmps: Return number of implemented context comparators.
+ * Note that the ID register CTX_CMPS field is "number of cmps - 1",
+ * and we return the actual number of comparators.
+ */
+static inline int arm_num_ctx_cmps(ARMCPU *cpu)
+{
+    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
+        return FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, CTX_CMPS) + 1;
+    } else {
+        return FIELD_EX32(cpu->dbgdidr, DBGDIDR, CTX_CMPS) + 1;
+    }
+}
+
 /* Note make_memop_idx reserves 4 bits for mmu_idx, and MO_BSWAP is bit 3.
  * Thus a TCGMemOpIdx, without any MO_ALIGN bits, fits in 8 bits.
  */
diff --git a/target/arm/debug_helper.c b/target/arm/debug_helper.c
index 2e3e90c6a57..2ff72d47d19 100644
--- a/target/arm/debug_helper.c
+++ b/target/arm/debug_helper.c
@@ -16,8 +16,8 @@ static bool linked_bp_matches(ARMCPU *cpu, int lbn)
 {
     CPUARMState *env = &cpu->env;
     uint64_t bcr = env->cp15.dbgbcr[lbn];
-    int brps = extract32(cpu->dbgdidr, 24, 4);
-    int ctx_cmps = extract32(cpu->dbgdidr, 20, 4);
+    int brps = arm_num_brps(cpu);
+    int ctx_cmps = arm_num_ctx_cmps(cpu);
     int bt;
     uint32_t contextidr;
     uint64_t hcr_el2;
@@ -29,7 +29,7 @@ static bool linked_bp_matches(ARMCPU *cpu, int lbn)
      * case DBGWCR<n>_EL1.LBN must indicate that breakpoint).
      * We choose the former.
      */
-    if (lbn > brps || lbn < (brps - ctx_cmps)) {
+    if (lbn >= brps || lbn < (brps - ctx_cmps)) {
         return false;
     }
 
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 11b87723e47..8415cc6b154 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6256,23 +6256,12 @@ static void define_debug_regs(ARMCPU *cpu)
     };
 
     /* Note that all these register fields hold "number of Xs minus 1". */
-    brps = extract32(cpu->dbgdidr, 24, 4);
-    wrps = extract32(cpu->dbgdidr, 28, 4);
-    ctx_cmps = extract32(cpu->dbgdidr, 20, 4);
+    brps = arm_num_brps(cpu);
+    wrps = arm_num_wrps(cpu);
+    ctx_cmps = arm_num_ctx_cmps(cpu);
 
     assert(ctx_cmps <= brps);
 
-    /* The DBGDIDR and ID_AA64DFR0_EL1 define various properties
-     * of the debug registers such as number of breakpoints;
-     * check that if they both exist then they agree.
-     */
-    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
-        assert(FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, BRPS) == brps);
-        assert(FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, WRPS) == wrps);
-        assert(FIELD_EX64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, CTX_CMPS)
-               == ctx_cmps);
-    }
-
     define_one_arm_cp_reg(cpu, &dbgdidr);
     define_arm_cp_regs(cpu, debug_cp_reginfo);
 
@@ -6280,7 +6269,7 @@ static void define_debug_regs(ARMCPU *cpu)
         define_arm_cp_regs(cpu, debug_lpae_cp_reginfo);
     }
 
-    for (i = 0; i < brps + 1; i++) {
+    for (i = 0; i < brps; i++) {
         ARMCPRegInfo dbgregs[] = {
             { .name = "DBGBVR", .state = ARM_CP_STATE_BOTH,
               .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = i, .opc2 = 4,
@@ -6299,7 +6288,7 @@ static void define_debug_regs(ARMCPU *cpu)
         define_arm_cp_regs(cpu, dbgregs);
     }
 
-    for (i = 0; i < wrps + 1; i++) {
+    for (i = 0; i < wrps; i++) {
         ARMCPRegInfo dbgregs[] = {
             { .name = "DBGWVR", .state = ARM_CP_STATE_BOTH,
               .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = i, .opc2 = 6,
