diff --git a/target/arm/translate.c b/target/arm/translate.c
index cb7b35489f..cb6296dc12 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -8491,6 +8491,39 @@ static bool trans_ERET(DisasContext *s, arg_ERET *a)
     return true;
 }
 
+static bool trans_HLT(DisasContext *s, arg_HLT *a)
+{
+    gen_hlt(s, a->imm);
+    return true;
+}
+
+static bool trans_BKPT(DisasContext *s, arg_BKPT *a)
+{
+    if (!ENABLE_ARCH_5) {
+        return false;
+    }
+    gen_exception_bkpt_insn(s, syn_aa32_bkpt(a->imm, false));
+    return true;
+}
+
+static bool trans_HVC(DisasContext *s, arg_HVC *a)
+{
+    if (!ENABLE_ARCH_7 || IS_USER(s) || arm_dc_feature(s, ARM_FEATURE_M)) {
+        return false;
+    }
+    gen_hvc(s, a->imm);
+    return true;
+}
+
+static bool trans_SMC(DisasContext *s, arg_SMC *a)
+{
+    if (!ENABLE_ARCH_6K || IS_USER(s) || arm_dc_feature(s, ARM_FEATURE_M)) {
+        return false;
+    }
+    gen_smc(s);
+    return true;
+}
+
 /*
  * Legacy decoder.
  */
@@ -8771,68 +8804,8 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
     } else if ((insn & 0x0f900000) == 0x01000000
                && (insn & 0x00000090) != 0x00000090) {
         /* miscellaneous instructions */
-        op1 = (insn >> 21) & 3;
-        sh = (insn >> 4) & 0xf;
-        rm = insn & 0xf;
-        switch (sh) {
-        case 0x0:
-            /* MSR/MRS (banked/register) */
-            /* All done in decodetree.  Illegal ops already signalled.  */
-            g_assert_not_reached();
-        case 0x1: /* bx, clz */
-        case 0x2: /* bxj */
-        case 0x3: /* blx */
-        case 0x4: /* crc32 */
-            /* All done in decodetree.  Illegal ops reach here.  */
-            goto illegal_op;
-        case 0x5: /* Saturating addition and subtraction.  */
-        case 0x6: /* ERET */
-            /* All done in decodetree.  Reach here for illegal ops.  */
-            goto illegal_op;
-        case 7:
-        {
-            int imm16 = extract32(insn, 0, 4) | (extract32(insn, 8, 12) << 4);
-            switch (op1) {
-            case 0:
-                /* HLT */
-                gen_hlt(s, imm16);
-                break;
-            case 1:
-                /* bkpt */
-                ARCH(5);
-                gen_exception_bkpt_insn(s, syn_aa32_bkpt(imm16, false));
-                break;
-            case 2:
-                /* Hypervisor call (v7) */
-                ARCH(7);
-                if (IS_USER(s)) {
-                    goto illegal_op;
-                }
-                gen_hvc(s, imm16);
-                break;
-            case 3:
-                /* Secure monitor call (v6+) */
-                ARCH(6K);
-                if (IS_USER(s)) {
-                    goto illegal_op;
-                }
-                gen_smc(s);
-                break;
-            default:
-                g_assert_not_reached();
-            }
-            break;
-        }
-        case 0x8:
-        case 0xa:
-        case 0xc:
-        case 0xe:
-            /* Halfword multiply and multiply accumulate.  */
-            /* All done in decodetree.  Reach here for illegal ops.  */
-            goto illegal_op;
-        default:
-            goto illegal_op;
-        }
+        /* All done in decodetree.  Illegal ops reach here.  */
+        goto illegal_op;
     } else if (((insn & 0x0e000000) == 0 &&
                 (insn & 0x00000090) != 0x90) ||
                ((insn & 0x0e000000) == (1 << 25))) {
@@ -10493,26 +10466,8 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
                     goto illegal_op;
 
                 if (insn & (1 << 26)) {
-                    if (arm_dc_feature(s, ARM_FEATURE_M)) {
-                        goto illegal_op;
-                    }
-                    if (!(insn & (1 << 20))) {
-                        /* Hypervisor call (v7) */
-                        int imm16 = extract32(insn, 16, 4) << 12
-                            | extract32(insn, 0, 12);
-                        ARCH(7);
-                        if (IS_USER(s)) {
-                            goto illegal_op;
-                        }
-                        gen_hvc(s, imm16);
-                    } else {
-                        /* Secure monitor call (v6+) */
-                        ARCH(6K);
-                        if (IS_USER(s)) {
-                            goto illegal_op;
-                        }
-                        gen_smc(s);
-                    }
+                    /* hvc, smc, in decodetree */
+                    goto illegal_op;
                 } else {
                     op = (insn >> 20) & 7;
                     switch (op) {
diff --git a/target/arm/a32.decode b/target/arm/a32.decode
index 52a66dd1d5..c7f156be6d 100644
--- a/target/arm/a32.decode
+++ b/target/arm/a32.decode
@@ -31,6 +31,7 @@
 &rrr             rd rn rm
 &rr              rd rm
 &r               rm
+&i               imm
 &msr_reg         rn r mask
 &mrs_reg         rd r
 &msr_bank        rn r sysm
@@ -196,9 +197,11 @@ CRC32CW          .... 0001 0100 .... .... 0010 0100 ....      @rndm
 # Miscellaneous instructions
 
 %sysm            8:1 16:4
+%imm16_8_0       8:12 0:4
 
 @rm              ---- .... .... .... .... .... .... rm:4      &r
 @rdm             ---- .... .... .... rd:4 .... .... rm:4      &rr
+@i16             ---- .... .... .... .... .... .... ....      &i imm=%imm16_8_0
 
 MRS_bank         ---- 0001 0 r:1 00 .... rd:4 001. 0000 0000  &mrs_bank %sysm
 MSR_bank         ---- 0001 0 r:1 10 .... 1111 001. 0000 rn:4  &msr_bank %sysm
@@ -213,3 +216,8 @@ BLX_r            .... 0001 0010 1111 1111 1111 0011 ....      @rm
 CLZ              .... 0001 0110 1111 .... 1111 0001 ....      @rdm
 
 ERET             ---- 0001 0110 0000 0000 0000 0110 1110
+
+HLT              .... 0001 0000 .... .... .... 0111 ....      @i16
+BKPT             .... 0001 0010 .... .... .... 0111 ....      @i16
+HVC              .... 0001 0100 .... .... .... 0111 ....      @i16
+SMC              ---- 0001 0110 0000 0000 0000 0111 imm:4     &i
diff --git a/target/arm/t32.decode b/target/arm/t32.decode
index 6236d28b99..5116c6165a 100644
--- a/target/arm/t32.decode
+++ b/target/arm/t32.decode
@@ -28,6 +28,7 @@
 &rrr             !extern rd rn rm
 &rr              !extern rd rm
 &r               !extern rm
+&i               !extern imm
 &msr_reg         !extern rn r mask
 &mrs_reg         !extern rd r
 &msr_bank        !extern rn r sysm
@@ -189,6 +190,7 @@ CLZ              1111 1010 1011 ---- 1111 .... 1000 ....      @rdm
 
 %msr_sysm        4:1 8:4
 %mrs_sysm        4:1 16:4
+%imm16_16_0      16:4 0:12
 
 {
   {
@@ -226,4 +228,7 @@ CLZ              1111 1010 1011 ---- 1111 .... 1000 ....      @rdm
     SUB_rri      1111 0011 1101 1110 1000 1111 imm:8 \
                  &s_rri_rot rot=0 s=1 rd=15 rn=14
   }
+  SMC            1111 0111 1111 imm:4 1000 0000 0000 0000     &i
+  HVC            1111 0111 1110 ....  1000 .... .... ....     \
+                 &i imm=%imm16_16_0
 }
