target/s390x: Add support for the TEST BLOCK instruction

TEST BLOCK was likely once used to execute basic memory
tests, but nowadays it's just a (slow) way to clear a page.
Reviewed-by: NAurelien Jarno <aurelien@aurel32.net>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Message-Id: <1495128400-23759-1-git-send-email-thuth@redhat.com>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

target/s390x/cpu.h

@@ -1084,6 +1084,7 @@ struct sysib_322 {
 #define SIGP_ORDER_MASK 0x000000ff
 
 void load_psw(CPUS390XState *env, uint64_t mask, uint64_t addr);
+target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr);
 int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc,
                   target_ulong *raddr, int *flags, bool exc);
 int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code);

target/s390x/helper.h

@@ -102,6 +102,7 @@ DEF_HELPER_FLAGS_4(lctl, TCG_CALL_NO_WG, void, env, i32, i64, i32)
 DEF_HELPER_FLAGS_4(lctlg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
 DEF_HELPER_FLAGS_4(stctl, TCG_CALL_NO_WG, void, env, i32, i64, i32)
 DEF_HELPER_FLAGS_4(stctg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
+DEF_HELPER_FLAGS_2(testblock, TCG_CALL_NO_WG, i32, env, i64)
 DEF_HELPER_FLAGS_2(tprot, TCG_CALL_NO_RWG, i32, i64, i64)
 DEF_HELPER_FLAGS_2(iske, TCG_CALL_NO_RWG_SE, i64, env, i64)
 DEF_HELPER_FLAGS_3(sske, TCG_CALL_NO_RWG, void, env, i64, i64)

target/s390x/insn-data.def

@@ -918,6 +918,8 @@
 /* STORE USING REAL ADDRESS */
     C(0xb246, STURA,   RRE,   Z,   r1_o, r2_o, 0, 0, stura, 0)
     C(0xb925, STURG,   RRE,   Z,   r1_o, r2_o, 0, 0, sturg, 0)
+/* TEST BLOCK */
+    C(0xb22c, TB,      RRE,   Z,   0, r2_o, 0, 0, testblock, 0)
 /* TEST PROTECTION */
     C(0xe501, TPROT,   SSE,   Z,   la1, a2, 0, 0, tprot, 0)
 

target/s390x/mem_helper.c

@@ -20,6 +20,7 @@
 
 #include "qemu/osdep.h"
 #include "cpu.h"
+#include "exec/address-spaces.h"
 #include "exec/helper-proto.h"
 #include "exec/exec-all.h"
 #include "exec/cpu_ldst.h"
@@ -973,6 +974,33 @@ void HELPER(stctl)(CPUS390XState *env, uint32_t r1, uint64_t a2, uint32_t r3)
     }
 }
 
+uint32_t HELPER(testblock)(CPUS390XState *env, uint64_t real_addr)
+{
+    CPUState *cs = CPU(s390_env_get_cpu(env));
+    uint64_t abs_addr;
+    int i;
+
+    real_addr = fix_address(env, real_addr);
+    abs_addr = mmu_real2abs(env, real_addr) & TARGET_PAGE_MASK;
+    if (!address_space_access_valid(&address_space_memory, abs_addr,
+                                    TARGET_PAGE_SIZE, true)) {
+        program_interrupt(env, PGM_ADDRESSING, 4);
+        return 1;
+    }
+
+    /* Check low-address protection */
+    if ((env->cregs[0] & CR0_LOWPROT) && real_addr < 0x2000) {
+        program_interrupt(env, PGM_PROTECTION, 4);
+        return 1;
+    }
+
+    for (i = 0; i < TARGET_PAGE_SIZE; i += 8) {
+        stq_phys(cs->as, abs_addr + i, 0);
+    }
+
+    return 0;
+}
+
 uint32_t HELPER(tprot)(uint64_t a1, uint64_t a2)
 {
     /* XXX implement */

target/s390x/mmu_helper.c

@@ -108,7 +108,7 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr,
  * Translate real address to absolute (= physical)
  * address by taking care of the prefix mapping.
  */
-static target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr)
+target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr)
 {
     if (raddr < 0x2000) {
         return raddr + env->psa;    /* Map the lowcore. */

target/s390x/translate.c

@@ -4062,6 +4062,16 @@ static ExitStatus op_tcxb(DisasContext *s, DisasOps *o)
 }
 
 #ifndef CONFIG_USER_ONLY
+
+static ExitStatus op_testblock(DisasContext *s, DisasOps *o)
+{
+    check_privileged(s);
+    potential_page_fault(s);
+    gen_helper_testblock(cc_op, cpu_env, o->in2);
+    set_cc_static(s);
+    return NO_EXIT;
+}
+
 static ExitStatus op_tprot(DisasContext *s, DisasOps *o)
 {
     potential_page_fault(s);
@@ -4069,6 +4079,7 @@ static ExitStatus op_tprot(DisasContext *s, DisasOps *o)
     set_cc_static(s);
     return NO_EXIT;
 }
+
 #endif
 
 static ExitStatus op_tr(DisasContext *s, DisasOps *o)