milkymist-minimac2: Use qemu_log_mask(GUEST_ERROR) instead of error_report

qemu_log_mask(GUEST_ERROR) is more appropriate:

  $ qemu -d help
  Log items (comma separated):
  guest_errors    log when the guest OS does something invalid (eg accessing a non-existent register)
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: NMichael Walle <michael@walle.cc>
Message-Id: <20181029130034.26750-1-f4bug@amsat.org>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

hw/net/milkymist-minimac2.c

@@ -30,6 +30,7 @@
 #include "hw/sysbus.h"
 #include "trace.h"
 #include "net/net.h"
+#include "qemu/log.h"
 #include "qemu/error-report.h"
 
 #include <zlib.h>
@@ -214,7 +215,8 @@ static size_t assemble_frame(uint8_t *buf, size_t size,
     uint32_t crc;
 
     if (size < payload_size + 12) {
-        error_report("milkymist_minimac2: received too big ethernet frame");
+        qemu_log_mask(LOG_GUEST_ERROR, "milkymist_minimac2: frame too big "
+                      "(%zd bytes)\n", payload_size);
         return 0;
     }
 
@@ -347,8 +349,9 @@ minimac2_read(void *opaque, hwaddr addr, unsigned size)
         break;
 
     default:
-        error_report("milkymist_minimac2: read access to unknown register 0x"
-                TARGET_FMT_plx, addr << 2);
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "milkymist_minimac2_rd%d: 0x%" HWADDR_PRIx "\n",
+                      size, addr << 2);
         break;
     }
 
@@ -413,8 +416,10 @@ minimac2_write(void *opaque, hwaddr addr, uint64_t value,
         break;
 
     default:
-        error_report("milkymist_minimac2: write access to unknown register 0x"
-                TARGET_FMT_plx, addr << 2);
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "milkymist_minimac2_wr%d: 0x%" HWADDR_PRIx
+                      " = 0x%" PRIx64 "\n",
+                      size, addr << 2, value);
         break;
     }
 }