UVM Reporting & Messaging

📋 The Four Severity Macros

UVM provides four severity levels for messages. Each has a default action — what the simulation does when that severity fires. Only `uvm_info messages are filtered by verbosity; the other three always print.

// ── Syntax for all four macros ────────────────────────────
// `uvm_info   (id, message, verbosity)
// `uvm_warning(id, message)
// `uvm_error  (id, message)
// `uvm_fatal  (id, message)

`uvm_info   ("DRV", $sformatf("Driving addr=0x%03h", addr), UVM_HIGH)
`uvm_warning("MON", "PREADY held low for > 16 cycles")
`uvm_error  ("SB",  $sformatf("MISMATCH exp=%0h act=%0h", exp, act))
`uvm_fatal  ("CFG", "No virtual interface in config_db!")

// ── Equivalent functional form (usable in classes and modules)
// When no 'this' context is available (e.g. inside covergroups)
uvm_report_info   ("ID", "message", UVM_MEDIUM);
uvm_report_warning("ID", "message");
uvm_report_error  ("ID", "message");
uvm_report_fatal  ("ID", "message");

📋 Verbosity Levels and the Filter Matrix

Verbosity controls which `uvm_info messages appear in the transcript. Each component has a verbosity setting; a message is printed only if its verbosity value is ≤ the component’s current verbosity setting. Lower verbosity = more important = always shown first.

Usage guidelines

📋 Setting Verbosity

Verbosity can be set globally, per component, or per message ID — from inside the testbench code or from the simulator command line without recompilation.

// ── Globally — all components ─────────────────────────────
// From start_of_simulation_phase or end_of_elaboration_phase
uvm_root::get().set_report_verbosity_level_hier(UVM_HIGH);

// ── Per component — just this one ────────────────────────
m_driver.set_report_verbosity_level(UVM_HIGH);

// ── Per component + all children ─────────────────────────
m_env.m_agent.set_report_verbosity_level_hier(UVM_FULL);

// ── Command line: global verbosity (no recompile) ────────
// +UVM_VERBOSITY=UVM_HIGH

// ── Command line: specific component ─────────────────────
// +uvm_set_verbosity=uvm_test_top.m_env.m_agent.m_drv,_ALL_,UVM_HIGH,run_phase
// Format: component_path, id, verbosity, phase (or "")  

// ── Query current verbosity ───────────────────────────────
int v = get_report_verbosity_level();

📋 Message Format and IDs

Every UVM message automatically includes the severity, simulation time, component path, and the ID string. Understanding the format helps decode regression log files quickly.

// ── What a typical UVM message looks like in the transcript
// UVM_INFO  @ 1450ns: uvm_test_top.env.agent.drv [DRV] Driving addr=0x004
// ─────────   ──────   ────────────────────────── ───   ──────────────────
// severity   time      component path              ID    message text
//
// UVM_ERROR @ 1500ns: uvm_test_top.env.sb [SB] MISMATCH exp=0xDEAD act=0xBEEF

// ── Good ID naming convention ─────────────────────────────
// Use component abbreviation as ID — easy to grep in logs
`uvm_info("DRV",  "...", UVM_HIGH)    // driver
`uvm_info("MON",  "...", UVM_MEDIUM)  // monitor
`uvm_info("SB",   "...", UVM_LOW)     // scoreboard
`uvm_info("SEQ",  "...", UVM_MEDIUM)  // sequence
`uvm_info("CFG",  "...", UVM_LOW)     // config
`uvm_info("TEST", "...", UVM_LOW)     // test

// ── Include class name in ID for precise location ─────────
`uvm_info({get_type_name(), "::run_phase"},
           "Starting driver", UVM_HIGH)
// → [apb_driver::run_phase] Starting driver

// ── Filter by ID from command line ───────────────────────
// +uvm_set_verbosity=uvm_test_top.env.agent.drv,DRV,UVM_HIGH,run
// Only shows UVM_HIGH DRV messages from the driver component

📋 uvm_report_enabled()

Some debug operations are expensive — calling item.print(), formatting a long string, or computing a diagnostic value. If these are guarded by a verbosity check, they are skipped unless the current verbosity level would display the result.

// ── Guard expensive operations with verbosity check ───────
task run_phase(uvm_phase phase);
  apb_seq_item item;
  forever begin
    seq_item_port.get_next_item(item);

    // Only call item.print() if UVM_HIGH would be displayed
    if (uvm_report_enabled(UVM_HIGH))
      item.print();   // skipped if verbosity < UVM_HIGH

    drive_transfer(item);
    seq_item_port.item_done();
  end
endtask

// ── Avoid expensive $sformatf when it won't be printed ────
if (uvm_report_enabled(UVM_FULL)) begin
  string dump = build_register_dump();  // only computed if needed
  `uvm_info("REG", dump, UVM_FULL)
end

📋 Error Count Thresholds

By default, UVM stops the simulation when 5 `uvm_error messages fire — the max_quit_count. This prevents a runaway test from generating thousands of error messages and filling log files. The threshold can be configured:

// ── Set max error count before stopping ───────────────────
// Default = 5. Set to 0 for unlimited (never stop on errors)
// Call from start_of_simulation_phase or build_phase
uvm_root::get().set_report_max_quit_count(20);   // stop after 20 errors
uvm_root::get().set_report_max_quit_count(0);    // never stop on errors

// ── Command line ──────────────────────────────────────────
// +UVM_MAX_QUIT_COUNT=20,YES

// ── Query current error and warning counts ────────────────
int err_count  = uvm_report_server::get_server().get_severity_count(UVM_ERROR);
int warn_count = uvm_report_server::get_server().get_severity_count(UVM_WARNING);

// ── Check counts in check_phase ───────────────────────────
function void check_phase(uvm_phase phase);
  int errs = uvm_report_server::get_server().get_severity_count(UVM_ERROR);
  if (errs > 0)
    `uvm_fatal("CHK", $sformatf("%0d errors during run", errs))
endfunction

📋 Report Hooks and Overrides

The report server allows overriding the default action for specific severity + ID combinations — for example, demoting expected errors to warnings, or promoting certain warnings to errors for a specific test.

// ── Override action for a specific ID ─────────────────────
// Actions: UVM_NO_ACTION, UVM_DISPLAY, UVM_COUNT, UVM_STOP, UVM_EXIT,
//          UVM_LOG (to file), UVM_RM_RECORD

// Demote UVM_ERROR for ID "SB" to just display (no count, no stop)
set_report_severity_id_override(UVM_ERROR, "SB", UVM_WARNING);

// Silence UVM_WARNING from monitor (expected during reset)
set_report_id_action(UVM_WARNING, "MON", UVM_NO_ACTION);

// Make a specific info message always print regardless of verbosity
set_report_severity_action(UVM_INFO, UVM_DISPLAY | UVM_COUNT);

// Redirect all errors to a log file AND display
int fd = $fopen("errors.log", "w");
set_report_severity_action(UVM_ERROR, UVM_DISPLAY | UVM_LOG);
set_report_default_file(fd);

// ── Per-component overrides ───────────────────────────────
m_driver.set_report_severity_action(UVM_WARNING, UVM_NO_ACTION);
// Silence all warnings from this driver

📋 Best Practices

📋 Quick Reference