diff --git a/exec.c b/exec.c
index 5fbeb8d..5ed63de 100644
--- a/exec.c
+++ b/exec.c
@@ -152,6 +152,7 @@
 char *logfilename = "/tmp/qemu.log";
 FILE *logfile;
 int loglevel;
+static int log_append = 0;
 
 /* statistics */
 static int tlb_flush_count;
@@ -1160,7 +1161,7 @@
 {
     loglevel = log_flags;
     if (loglevel && !logfile) {
-        logfile = fopen(logfilename, "w");
+        logfile = fopen(logfilename, log_append ? "wa" : "w");
         if (!logfile) {
             perror(logfilename);
             _exit(1);
@@ -1174,12 +1175,22 @@
 #else
         setvbuf(logfile, NULL, _IOLBF, 0);
 #endif
+        log_append = 1;
+    }
+    if (!loglevel && logfile) {
+        fclose(logfile);
+        logfile = NULL;
     }
 }
 
 void cpu_set_log_filename(const char *filename)
 {
     logfilename = strdup(filename);
+    if (logfile) {
+        fclose(logfile);
+        logfile = NULL;
+    }
+    cpu_set_log(loglevel);
 }
 
 /* mask must never be zero, except for A20 change call */
diff --git a/monitor.c b/monitor.c
index a8db870..ed31d50 100644
--- a/monitor.c
+++ b/monitor.c
@@ -406,6 +406,11 @@
     vga_hw_screen_dump(filename);
 }
 
+static void do_logfile(const char *filename)
+{
+    cpu_set_log_filename(filename);
+}
+
 static void do_log(const char *items)
 {
     int mask;
@@ -1213,6 +1218,8 @@
       "device filename", "change a removable medium" },
     { "screendump", "F", do_screen_dump, 
       "filename", "save screen into PPM image 'filename'" },
+    { "logfile", "s", do_logfile,
+      "filename", "output logs to 'filename'" },
     { "log", "s", do_log,
       "item1[,...]", "activate logging of the specified items to '/tmp/qemu.log'" }, 
     { "savevm", "s?", do_savevm,