Use of $urandom()

In core-v-verif there are 8 files that use some variation of $urandom(). You are in the "assignees" list of this issue because git believes you authored one or more of these.

The Verissimo linter flags these as violation SVTB.29.1.3.1, which is a lint error because class members randomized with these calls cannot be constrained. I also worry that invocations of $urandom() may impair random stability (that is, the ability to reproduce results from the same seed).

Possible resolutions:

1. Accept the use of $urandom() and create a project-wide waiver for SVTB.29.1.3.1.
2. Enforce the use of a configuration or context class of random members to implement the same functionality.
3. Waive, or not, on a case-by-case basis.

Example fixes

From uvma_obi_memory_drv.sv. Replace this:

UVMA_OBI_MEMORY_DRV_IDLE_RANDOM: begin
   `uvm_info("OBI_MEMORY_DRV", $sformatf("Invalid drv_random: %0d", cfg.drv_idle), UVM_NONE)
   slv_mp.drv_slv_cb.rdata <= $urandom();
   slv_mp.drv_slv_cb.err   <= $urandom();
   slv_mp.drv_slv_cb.ruser <= $urandom();
   slv_mp.drv_slv_cb.rid   <= $urandom();
end

...with this:

UVMA_OBI_MEMORY_DRV_IDLE_RANDOM: begin
   `uvm_info("OBI_MEMORY_DRV", $sformatf("Invalid drv_random: %0d", cfg.drv_idle), UVM_NONE)
   if (!obi_mem_drv_random_cntxt.randomize())
      `uvm_error("OBI_MEMORY_DRV", "Cannot randomize obi_mem_drv_random_cntxt")
   slv_mp.drv_slv_cb.rdata <= obi_mem_drv_random_cntxt.rdata;
   slv_mp.drv_slv_cb.err   <= obi_mem_drv_random_cntxt.err;
   slv_mp.drv_slv_cb.ruser <= obi_mem_drv_random_cntxt.ruser;
   slv_mp.drv_slv_cb.rid   <= obi_mem_drv_random_cntxt.rid;
end

Steps to Reproduce

Lint checks are run every six hours - the link above will show all violations of this rule.

Additional context

This is a set of linter issues identified by the Verissimo SystemVerilog Testbench Linter. Please reach out to me directly if you have questions about the tool.