[PATCH v3 17/20] util: add support for formatting a workload name in messages

["Daniel P. Berrangé" <berrange@redhat.com>]

The error_report function can include the guest name in any
messages it prints. The qemu_log function has no equivalent
behaviour.

This introduces support for a "workload name" in the new
messages API, which in the case of system emulators will
be the guest name. The possibility of defining a workload
name for other binaries is left as an exercise for the
future.

This change has no impact on the output of the error_report
function, but will change the qemu_log function. This can
be easily seen with the 'log' trace backend, and how it is
now more closely matching error_report output.

Before:

  # qemu-system-x86_64 -msg guest-name=on -name blah -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55b3af3fd870 dir=fish
  qcrypto_tls_creds_get_path TLS creds path creds=0x55b3af3fd870 filename=ca-cert.pem path=<none>
  blah qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

After:

  # qemu-system-x86_64 -msg guest-name=on -name blah -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  blah qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55b3af3fd870 dir=fish
  blah qcrypto_tls_creds_get_path TLS creds path creds=0x55b3af3fd870 filename=ca-cert.pem path=<none>
  blah qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/error-report.h |  3 ---
 include/qemu/message.h      | 10 ++++++++++
 system/vl.c                 |  6 ++++--
 util/error-report.c         |  7 -------
 util/message.c              | 12 +++++++++++-
 5 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index c8000778ec..ffc305f828 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -70,7 +70,4 @@ void error_init(const char *argv0);
                               fmt, ##__VA_ARGS__);      \
     })
 
-extern bool error_with_guestname;
-extern const char *error_guest_name;
-
 #endif
diff --git a/include/qemu/message.h b/include/qemu/message.h
index 0a06421f77..cfc3c92648 100644
--- a/include/qemu/message.h
+++ b/include/qemu/message.h
@@ -5,6 +5,7 @@
 
 enum QMessageFormatFlags {
     QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
+    QMESSAGE_FORMAT_WORKLOAD_NAME = (1 << 1),
 };
 
 /**
@@ -16,6 +17,15 @@ enum QMessageFormatFlags {
  */
 void qmessage_set_format(int flags);
 
+/**
+ * qmessage_set_workload_name:
+ * @name: the name of the workload
+ *
+ * Set the workload name, which for a system emulator
+ * will be the guest VM name.
+ */
+void qmessage_set_workload_name(const char *name);
+
 /**
  * qmessage_context_print:
  * @fp: file to emit the prefix on
diff --git a/system/vl.c b/system/vl.c
index 696dd92669..fee6fdf7b1 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -818,7 +818,9 @@ static void configure_msg(QemuOpts *opts)
     if (qemu_opt_get_bool(opts, "timestamp", false)) {
         flags |= QMESSAGE_FORMAT_TIMESTAMP;
     }
-    error_with_guestname = qemu_opt_get_bool(opts, "guest-name", false);
+    if (qemu_opt_get_bool(opts, "guest-name", false)) {
+        flags |= QMESSAGE_FORMAT_WORKLOAD_NAME;
+    }
     qmessage_set_format(flags);
 }
 
@@ -3520,7 +3522,7 @@ void qemu_init(int argc, char **argv)
                     exit(1);
                 }
                 /* Capture guest name if -msg guest-name is used later */
-                error_guest_name = qemu_opt_get(opts, "guest");
+                qmessage_set_workload_name(qemu_opt_get(opts, "guest"));
                 break;
             case QEMU_OPTION_prom_env:
                 if (nb_prom_envs >= MAX_PROM_ENVS) {
diff --git a/util/error-report.c b/util/error-report.c
index 719f059494..c40cdf3bb3 100644
--- a/util/error-report.c
+++ b/util/error-report.c
@@ -25,8 +25,6 @@ typedef enum {
     REPORT_TYPE_INFO,
 } report_type;
 
-bool error_with_guestname;
-const char *error_guest_name;
 
 typedef void (*error_print_func)(void *opaque, const char *fmt, ...);
 typedef void (*error_print_vfunc)(void *opaque, const char *fmt, va_list ap);
@@ -218,11 +216,6 @@ static void vreport(report_type type, const char *fmt, va_list ap)
         qmessage_context_print(stderr);
     }
 
-    /* Only prepend guest name if -msg guest-name and -name guest=... are set */
-    if (error_with_guestname && error_guest_name && !cur) {
-        print_func(print_opaque, "%s ", error_guest_name);
-    }
-
     print_loc(!!cur, print_func, print_opaque);
 
     switch (type) {
diff --git a/util/message.c b/util/message.c
index ef70e08c5f..a91c008e08 100644
--- a/util/message.c
+++ b/util/message.c
@@ -6,18 +6,28 @@
 #include "monitor/monitor.h"
 
 static int message_format;
+static char *message_workloadname;
 
 void qmessage_set_format(int flags)
 {
     message_format = flags;
 }
 
-void qmessage_context_print(FILE *fp)
+void qmessage_set_workload_name(const char *name)
 {
+    message_workloadname = g_strdup(name);
+}
 
+void qmessage_context_print(FILE *fp)
+{
     if (message_format & QMESSAGE_FORMAT_TIMESTAMP) {
         g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
         g_autofree char *timestr = g_date_time_format_iso8601(dt);
         fprintf(fp, "%s ", timestr);
     }
+
+    if ((message_format & QMESSAGE_FORMAT_WORKLOAD_NAME) &&
+        message_workloadname) {
+        fprintf(fp, "%s ", message_workloadname);
+    }
 }
-- 
2.50.1