This series is a tangent that came out of discussion in https://lists.nongnu.org/archive/html/qemu-devel/2025-08/msg00903.html In thinking about adding thread info to error_report, I came to realize we should likely make qemu_log behave consistently with error_report & friends. We already honour '-msg timestamp=on', but don't honour 'guest-name=on' and also don't include the binary name. As an example of the current state, consider mixing error and log output today: - Default context: # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \ -d 'trace:qcrypto*' qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55ac6d97f700 dir=fish qcrypto_tls_creds_get_path TLS creds path creds=0x55ac6d97f700 filename=ca-cert.pem path=<none> qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory - Full context: # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \ -d 'trace:qcrypto*' \ -msg guest-name=on,timestamp=on \ -name "fish food" 2025-08-19T20:14:16.791413Z qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55e9a3458d10 dir=fish 2025-08-19T20:14:16.791429Z qcrypto_tls_creds_get_path TLS creds path creds=0x55e9a3458d10 filename=ca-cert.pem path=<none> 2025-08-19T20:14:16.791433Z fish food qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory And after this series is complete: - Default context: # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \ -d 'trace:qcrypto*' qemu-system-x86_64(1184284:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55a24ad5cb30 dir=fish qemu-system-x86_64(1184284:main): qcrypto_tls_creds_get_path TLS creds path creds=0x55a24ad5cb30 filename=ca-cert.pem path=<none> qemu-system-x86_64(1184284:main): Unable to access credentials fish/ca-cert.pem: No such file or directory - Full context: # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \ -d 'trace:qcrypto*' \ -msg guest-name=on,timestamp=on \ -name "fish food" 2025-08-19T20:12:50.211823Z [fish food] qemu-system-x86_64(1168876:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5582183d8760 dir=fish 2025-08-19T20:12:50.211842Z [fish food] qemu-system-x86_64(1168876:main): qcrypto_tls_creds_get_path TLS creds path creds=0x5582183d8760 filename=ca-cert.pem +path=<none> 2025-08-19T20:12:50.211846Z [fish food] qemu-system-x86_64(1168876:main): Unable to access credentials fish/ca-cert.pem: No such file or directory The main things to note: * error_report/warn_report/qemu_log share the same output format and -msg applies to both * -msg debug-threads=on is now unconditionally enabled and thus the param is deprecated & ignored * Thread ID and name are unconditionally enabled * Guest name is surrounded in [...] brackets * The default output lines are typically 15 chars wider given that we always include the thread ID + name now * This takes the liberty of assigning the new file to the existing error-report.c maintainer (Markus) Since splitting it off into message.c instead of putting it all in error-report.c felt slightly nicer. One thing I didn't tackle is making the location info get reported for qemu_log. This is used to give context for error messages when parsing some CLI args, and could be interesting for log messages associated with those same CLI args. Changes in v4: - Re-architected the way error_vprintf() operates to simplify monitor dependency - Fixed the move of error_vprintf from monitor.c to error-report.c so that unit tests can still get a stub to capture messages to g_test_message - Simplify changes to vreport() to avoid passing around function pointers - Add locking of stderr to vreport() to serialize incremental output - Fix thread naming logic changes on Windows - Change deprecation warning messages Changes in v3: - Stop formatting a string in qmessage_context, instead output directly to a "FILE *" stream - Fix pre-existing bug interleaving qemu_log and vreport when the trace 'log' backend has mutex probes enabled Changes in v2: - Re-use existing qemu_get_thread_id rather than re-inventing it as qemu_thread_get_id. - Expose qemu_thread_set_name and use it from all locations needing to set thread names - Fix qemu_log() to skip context prefix when emitting a log message in fragments across multiple calls - Skip allocating memory for empty context messages - Fix leak in win32 impl of qemu_thread_get_name - Use g_strlcpy where possible Daniel P. Berrangé (23): include: define constant for early constructor priority monitor: initialize global data from a constructor system: unconditionally enable thread naming util: expose qemu_thread_set_name audio: make jackaudio use qemu_thread_set_name util: set the name for the 'main' thread util: add API to fetch the current thread name log: avoid repeated prefix on incremental qemu_log calls util: introduce some API docs for logging APIs ui/vnc: remove use of error_printf_unless_qmp() monitor: remove redundant error_[v]printf_unless_qmp monitor: refactor error_vprintf() monitor: move error_vprintf back to error-report.c monitor: introduce monitor_cur_is_hmp() helper util: don't skip error prefixes when QMP is active util: fix interleaving of error & trace output util: fix interleaving of error prefixes util: introduce common helper for error-report & log code util: convert error-report & log to message API for timestamp util: add support for formatting a workload name in messages util: add support for formatting a program name in messages util: add support for formatting thread info in messages util: add brackets around guest name in message context MAINTAINERS | 2 + audio/jackaudio.c | 30 +++++++-- docs/about/deprecated.rst | 7 ++ include/monitor/monitor.h | 4 +- include/qemu/compiler.h | 8 +++ include/qemu/error-report.h | 4 -- include/qemu/log-for-trace.h | 35 +++++++++- include/qemu/log.h | 26 ++++++++ include/qemu/message.h | 40 ++++++++++++ include/qemu/thread.h | 3 +- meson.build | 21 ++++++ monitor/monitor.c | 61 ++++++----------- rust/util/src/log.rs | 7 ++ storage-daemon/qemu-storage-daemon.c | 6 ++ stubs/error-printf.c | 23 ------- stubs/meson.build | 1 - stubs/monitor-core.c | 20 +++++- system/vl.c | 31 ++++++--- tests/qemu-iotests/041 | 2 +- tests/qemu-iotests/common.filter | 2 +- tests/unit/test-error-report.c | 6 +- tests/unit/test-util-sockets.c | 1 + ui/vnc.c | 14 ++-- util/error-report.c | 97 +++++++++++++++++----------- util/log.c | 28 ++++---- util/meson.build | 1 + util/message.c | 47 ++++++++++++++ util/qemu-thread-posix.c | 77 +++++++++++++++------- util/qemu-thread-win32.c | 87 +++++++++++++++++-------- 29 files changed, 485 insertions(+), 206 deletions(-) create mode 100644 include/qemu/message.h delete mode 100644 stubs/error-printf.c create mode 100644 util/message.c -- 2.50.1