target/mips/op_helper: Log unimplemented cache opcode

In case the guest uses a cache opcode we are not expecting,
log it to give us a chance to notice it, in case we should
actually do something.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <20200813181527.22551-4-f4bug@amsat.org>

target/mips/op_helper.c

@@ -1574,6 +1574,13 @@ void helper_msa_st_d(CPUMIPSState *env, uint32_t wd,
 void helper_cache(CPUMIPSState *env, target_ulong addr, uint32_t op)
 {
 #ifndef CONFIG_USER_ONLY
+    static const char *const type_name[] = {
+        "Primary Instruction",
+        "Primary Data or Unified Primary",
+        "Tertiary",
+        "Secondary"
+    };
+    uint32_t cache_type = extract32(op, 0, 2);
     uint32_t cache_operation = extract32(op, 2, 3);
     target_ulong index = addr & 0x1fffffff;
 
@@ -1592,6 +1599,8 @@ void helper_cache(CPUMIPSState *env, target_ulong addr, uint32_t op)
         /* no-op */
         break;
     default:
+        qemu_log_mask(LOG_UNIMP, "cache operation:%u (type: %s cache)\n",
+                      cache_operation, type_name[cache_type]);
         break;
     }
 #endif