Config Resolution Order: Precedence When Sets Compete

Resolution model

When multiple sets target the same field for the same consumer, config_db applies path specificity first , then considers hierarchy position. Sets from higher in the tree (test, top) typically override VIP defaults set lower.

[CONFIG] precedence (consumer at uvm_test_top.env.apb.drv)

  Priority 1: Exact path match
    uvm_test_top.env.apb.drv + "timeout"

  Priority 2: Wildcard path match (most specific wildcard wins)
    uvm_test_top.env.apb.*   + "timeout"
    uvm_test_top.env.*       + "timeout"

  Priority 3: Global fallback
    *                        + "timeout"

  Higher hierarchy set typically beats lower VIP default set

Competing sets example

// VIP agent default (set in agent package init or agent build)
uvm_config_db#(int)::set(this, "*", "timeout", 500);

// Test override — wins for all agents under env
uvm_config_db#(int)::set(this, "env.*", "timeout", 2000);

// Surgical override — wins only for apb0 driver
uvm_config_db#(int)::set(this, "env.apb0.drv", "timeout", 50);

[UVM] effective timeout per component

  env.apb0.drv   → 50     (exact path wins)
  env.apb0.mon   → 2000   (env.* wildcard)
  env.apb1.drv   → 2000   (env.* wildcard)
  env.i2c.drv    → 2000   (env.* beats agent * default of 500)

exists() and introspection

Use exists() to probe whether a field is set without retrieving the value:

if (uvm_config_db#(int)::exists(this, "", "timeout"))
  `uvm_info("CFG", "timeout is set", UVM_LOW)

// Dump all config entries (verbose — use during debug)
uvm_config_db::dump();

• exists() is useful for optional config with documented defaults.

• dump() shows all entries — essential for path mismatch triage.

• Print get_full_name() alongside dump output to correlate paths.

Key takeaways

• More-specific paths win over broader wildcards.

• Test-level sets typically override VIP package defaults.

• Use exists() and dump() when resolution behavior is unclear.

Common pitfalls

• Assuming last-set-wins globally — specificity rules apply, not order alone.

• VIP default * set shadowing test intent due to wrong path specificity.

• Not dumping config when two teams set the same field name differently.