qemu-log: Open file for logging when specified

qemu-log defaults to stderr when there is no '-D' option mentioned on command
line. When '-D' option is specified, we also need to specify '-d' option for it
to use the specified logfile. When using monitor to enable logging this is
troublesome since there will be no '-d' option because of which monitor dumps
the logs to stderr.

Fix this by opening the log file when '-D' is specified on the command line.
Also fix an ancient comment which does not hold true since changing location and
log level has now been streamlined.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Luiz Capitulino <lcapitulino@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1433946024-18439-1-git-send-email-bobby.prani@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 5 insertions, 8 deletions

diff --git a/vl.c b/vl.c
index 2201e27fdc..63ce07f478 100644
--- a/vl.c
+++ b/vl.c
@@ -3916,17 +3916,14 @@ int main(int argc, char **argv, char **envp)
         exit(0);
     }
 
-    /* Open the logfile at this point, if necessary. We can't open the logfile
-     * when encountering either of the logging options (-d or -D) because the
-     * other one may be encountered later on the command line, changing the
-     * location or level of logging.
+    /* Open the logfile at this point and set the log mask if necessary.
      */
+    if (log_file) {
+        qemu_set_log_filename(log_file);
+    }
+
     if (log_mask) {
         int mask;
-        if (log_file) {
-            qemu_set_log_filename(log_file);
-        }
-
         mask = qemu_str_to_log_mask(log_mask);
         if (!mask) {
             qemu_print_log_usage(stdout);