Two useful aspects for observability:
1. Logging
Error messages, rate-limited warnings, and important troubleshooting
information for users.
Audience: Users, system administrators, developers
2. Tracing
Internal state changes and events for performance analysis.
Audience: Developers
DPRINTF() falls under both #1 and #2. Care needs to be taken to
separate the logging from the tracing when converting DPRINTF().
Side note: we don't have effect "once only" or rate-limiting built into
error_report(). Guest-triggerable errors or warnings should be limited
to prevent log flooding.
It would be nice to unify TCG's "qemu log" and error_report() into a
single logging mechanism that is thread-safe and has rate-limiting.
Stefan