diff --git a/target-s390x/helper.h b/target-s390x/helper.h
index 7e048ec..6be9f44 100644
--- a/target-s390x/helper.h
+++ b/target-s390x/helper.h
@@ -87,7 +87,7 @@
 
 #ifndef CONFIG_USER_ONLY
 DEF_HELPER_3(servc, i32, env, i64, i64)
-DEF_HELPER_4(diag, i64, env, i32, i64, i64)
+DEF_HELPER_4(diag, void, env, i32, i32, i32)
 DEF_HELPER_3(load_psw, noreturn, env, i64, i64)
 DEF_HELPER_FLAGS_2(spx, TCG_CALL_NO_RWG, void, env, i64)
 DEF_HELPER_FLAGS_1(stck, TCG_CALL_NO_RWG_SE, i64, env)
diff --git a/target-s390x/insn-data.def b/target-s390x/insn-data.def
index 1223670..fe5e591 100644
--- a/target-s390x/insn-data.def
+++ b/target-s390x/insn-data.def
@@ -835,7 +835,7 @@
 /* COMPARE AND SWAP AND PURGE */
     C(0xb250, CSP,     RRE,   Z,   0, ra2, 0, 0, csp, 0)
 /* DIAGNOSE (KVM hypercall) */
-    C(0x8300, DIAG,    RX_a,  Z,   0, 0, 0, 0, diag, 0)
+    C(0x8300, DIAG,    RSI,   Z,   0, 0, 0, 0, diag, 0)
 /* INSERT STORAGE KEY EXTENDED */
     C(0xb229, ISKE,    RRE,   Z,   0, r2_o, new, r1_8, iske, 0)
 /* INVALIDATE PAGE TABLE ENTRY */
diff --git a/target-s390x/misc_helper.c b/target-s390x/misc_helper.c
index 6711504..eebe608 100644
--- a/target-s390x/misc_helper.c
+++ b/target-s390x/misc_helper.c
@@ -205,9 +205,15 @@
     switch (subcode) {
     case 0:
         modified_clear_reset(s390_env_get_cpu(env));
+        if (tcg_enabled()) {
+            cpu_loop_exit(CPU(s390_env_get_cpu(env)));
+        }
         break;
     case 1:
         load_normal_reset(s390_env_get_cpu(env));
+        if (tcg_enabled()) {
+            cpu_loop_exit(CPU(s390_env_get_cpu(env)));
+        }
         break;
     case 5:
         if ((r1 & 1) || (addr & 0x0fffULL)) {
@@ -254,9 +260,7 @@
 }
 #endif
 
-/* DIAG */
-uint64_t HELPER(diag)(CPUS390XState *env, uint32_t num, uint64_t mem,
-                      uint64_t code)
+void HELPER(diag)(CPUS390XState *env, uint32_t r1, uint32_t r3, uint32_t num)
 {
     uint64_t r;
 
@@ -271,6 +275,7 @@
         break;
     case 0x308:
         /* ipl */
+        handle_diag_308(env, r1, r3);
         r = 0;
         break;
     default:
@@ -281,8 +286,6 @@
     if (r) {
         program_interrupt(env, PGM_OPERATION, ILEN_LATER_INC);
     }
-
-    return r;
 }
 
 /* Set Prefix */
diff --git a/target-s390x/translate.c b/target-s390x/translate.c
index 9b87714..bde5e8a 100644
--- a/target-s390x/translate.c
+++ b/target-s390x/translate.c
@@ -2025,15 +2025,19 @@
 #ifndef CONFIG_USER_ONLY
 static ExitStatus op_diag(DisasContext *s, DisasOps *o)
 {
-    TCGv_i32 tmp;
+    TCGv_i32 r1 = tcg_const_i32(get_field(s->fields, r1));
+    TCGv_i32 r3 = tcg_const_i32(get_field(s->fields, r3));
+    TCGv_i32 func_code = tcg_const_i32(get_field(s->fields, i2));
 
     check_privileged(s);
-    potential_page_fault(s);
+    update_psw_addr(s);
+    gen_op_calc_cc(s);
 
-    /* We pretend the format is RX_a so that D2 is the field we want.  */
-    tmp = tcg_const_i32(get_field(s->fields, d2) & 0xfff);
-    gen_helper_diag(regs[2], cpu_env, tmp, regs[2], regs[1]);
-    tcg_temp_free_i32(tmp);
+    gen_helper_diag(cpu_env, r1, r3, func_code);
+
+    tcg_temp_free_i32(func_code);
+    tcg_temp_free_i32(r3);
+    tcg_temp_free_i32(r1);
     return NO_EXIT;
 }
 #endif