Comportable IP Testbench Architecture

Overview

Going along the lines of what it takes to design an IP that adheres to the Comportability Specifications, we attempt to standardize the DV methodology for developing the IP level testbench environment as well by following the same approach. This document describes the Comportable IP (CIP) library, which is a complete UVM environment framework that each IP level environment components can extend from to get started with DV. The goal here is to maximize code reuse across all test benches so that we can improve the efficiency and time to market. The features described here are not exhaustive, so it is highly recommended to the reader that they examine the code directly. In course of development, we also periodically identify pieces of verification logic that might be developed for one IP but is actually a good candidate to be added to these library classes instead. This doc is instead intended to provide the user a foray into what these are and how are the meant to be used.

CIP environment block diagram

CIP library classes

The CIP library includes the base ral model, env cfg object, coverage object, virtual sequencer, scoreboard, env, base virtual sequence and finally the test class. To achieve run-time polymorphism, these classes are type parameterized to indicate what type of child objects are to be created. In the IP environments, the extended classes indicate the correct type parameters.

cip_base_env_cfg

This class is intended to contain all of the settings, knobs, features, interface handles and downstream agent cfg handles. Features that are common to all IPs in accordance with the comportability spec are made a part of this base class, while the extended IP env cfg class will contain settings specific to that IP. An instance of the env cfg class is created in cip_base_test::build_phase and the handle is passed over uvm_config_db for the CIP env components to pick up. This allows the handle to the env cfg object to be available in the env's build_phase. Settings in the env cfg can then be used to configure the env based on the test needs.

A handle to this class instance is passed on to the scoreboard, virtual sequencer and coverage objects so that all such common settings and features are instantly accessible everywhere.

This class is type parameterized in the following way:

class cip_base_env_cfg #(type RAL_T = dv_base_reg_block) extends uvm_object;

The IP env cfg class will then extend from this class with the RAL_T parameter set to the actual IP RAL model class. This results in IP RAL model getting factory overridden automatically in the base env cfg itself during creation, so there is no need for manual factory override. We follow the same philosophy in all CIP library classes.

The following is a list of common features and settings:

clk_rst_if: A handle to the clk_rst_if that controls the main clk and reset to the DUT.
intr_vif: This is a handle to the pins_if #(NUM_MAX_INTERRUPTS=64) interface instance created in the tb to hookup the DUT interrupts. The actual number of interrupts might be much less than 64, but that is ok - we just connect as many as the DUT provides. The reason for going with a fixed width pins_if is to allow the intr_vif to be available in this base env cfg class (which does not know how many interrupt each IP DUT provides).
devmode_vif: This is a handle to the pins_if #(1) interface instance created in the tb to hookup the DUT input devmode.
tl_agent_cfg: The downstream TileLink host agent created in the cip_base_env class requires the agent cfg handle to tell it how to configure the agent.
alert_agent_cfgs: Similar to tl_agent_cfg, the downstream alert device agent created in the cip_base_env class requires the agent cfg handles to tell it how to configure the agent. In default, alert agent is configured in device mode, asynchronous, active and the ping coverage is turned off.
ral: This is the instance to the auto-generated RAL model that is extended from dv_base_reg_block. In the base class, this is created using the RAL_T class parameter which the extended IP env cfg class sets correctly.
tl_intg_alert_name: Name of the alert that will be triggered on TLUL integrity error detection. The default name used for this type of alert is “fatal_fault”. The block may use a different name too - in that case, please update this member to reflect the correct name in the initialize() method.
tl_intg_alert_fields: An associative array of CSR fields keyed with the objection handle of the corresponding CSR field and valued with the expected value. This is the list of CSR fields that are modified when an alert triggers due to TL integrity violation event. The DV user is required to build this list in the initialize() method after super.initialize(csr_base_addr);

virtual function void initialize(bit [31:0] csr_base_addr = '1);
  super.initialize(csr_base_addr); // ral model is created in `super.initialize`
  tl_intg_alert_fields[ral.a_status_reg.a_field] = value;

Apart from these, there are several common settings such as zero_delays, clk_freq_mhz, which are randomized as well as knobs such as en_scb and en_cov to turn on/off scoreboard and coverage collection respectively.

The base class provides a virtual method called initialize() which is called in cip_base_test::build_phase to create some of the objects listed above. If the extended IP env cfg class has more such objects added, then the initialize() method is required to be overridden to create those objects as well.

We make all downstream interface agent cfg handles as a part of IP extension of cip_base_env_cfg so that all settings for the env and all downstream agents are available within the env cfg handle. Since the env cfg handle is passed to all cip components, all those settings are also accessible.

cip_base_env_cov

This is the base coverage object that contain all functional coverpoints and covergroups. The main goal is to have all functional coverage elements implemented in a single place. This class is extended from uvm_component so that it allows items to be set via 'uvm_config_db using the component's hierarchy. This is created in cip_base_env and a handle to it is passed to the scoreboard and the virtual sequencer. This allows coverage to be sampled in scoreboard as well as the test sequences.

This class is type parameterized with the env cfg class type CFG_T so that it can derive coverage on some of the env cfg settings.

class cip_base_env_cov #(type CFG_T = cip_base_env_cfg) extends uvm_component;

The following covergroups are defined outside of the class for use by all IP testbenches:

intr_cg: Covers individual and cross coverage on intr_enable and intr_state for all interrupts in IP
intr_test_cg: Covers intr_test coverage and its cross with intr_enable and intr_state for all interrupts in IP
intr_pins_cg: Covers values and transitions on all interrupt output pins of IP
sticky_intr_cov: Covers sticky interrupt functionality of all applicable interrupts in IP

Covergroups intr_cg, intr_test_cg and intr_pins_cg are instantiated and allocated in cip_base_env_cov by default in all IPs. On the other hand, sticky_intr_cov is instantiated with string key. The string key represents the interrupts names that are sticky. This is specific to each IP and is required to be created and instantiated in extended cov class.

cip_base_virtual_sequencer

This is the base virtual sequencer class that contains a handle to the tl_sequencer to allow layered test sequences to be created. The extended IP virtual sequencer class will include handles to the IP specific agent sequencers.

This class is type-parameterized with the env cfg class type CFG_T and coverage class type COV_T so that all test sequences can access the env cfg settings and sample the coverage via the p_sequencer handle.

class cip_base_virtual_sequencer #(type CFG_T = cip_base_env_cfg,
                                   type COV_T = cip_base_env_cov) extends uvm_sequencer;

cip_base_scoreboard

This is the base scoreboard component that already connects with the TileLink agent monitor to grab tl packets via analysis port at the address and the data phases. It provides a virtual task called process_tl_access that the extended IP scoreboard needs to implement. Please see code for additional details. The extended IP scoreboard class will connect with the IP-specific interface monitors if applicable to grab items from those analysis ports.

This class is type-parameterized with the env cfg class type CFG_T, ral class type RAL_T and the coverage class type COV_T.

class cip_base_scoreboard #(type RAL_T = dv_base_reg_block,
                            type CFG_T = cip_base_env_cfg,
                            type COV_T = cip_base_env_cov) extends uvm_component;

There are several virtual tasks and functions that are to be overridden in extended IP scoreboard class. Please take a look at the code for more details.

cip_base_env

This is the base UVM env that puts all of the above components together and creates and makes connections across them. In the build phase, it retrieves the env cfg class type handle from uvm_config_db as well as all the virtual interfaces (which are actually part of the env cfg class). It then uses the env cfg settings to modify the downstream agent cfg settings as required. All of the above components are created based on env cfg settings, along with the TileLink host agent and alert device agents if the module has alerts. In the connect phase, the scoreboard connects with the monitor within the TileLink agent to be able to grab packets from the TL interface during address and the data phases. The scoreboard also connects the alert monitor within the alert_esc_agent to grab packets regarding alert handshake status. In the end of elaboration phase, the ral model within the env cfg handle is locked and the ral sequencer and adapters are set to be used with the TileLink interface.

This class is type parameterized with env cfg class type CFG_T, coverage class type COV_T, virtual sequencer class type VIRTUAL_SEQUENCER_T and scoreboard class type SCOREBOARD_T.

class cip_base_env #(type CFG_T               = cip_base_env_cfg,
                     type VIRTUAL_SEQUENCER_T = cip_base_virtual_sequencer,
                     type SCOREBOARD_T        = cip_base_scoreboard,
                     type COV_T               = cip_base_env_cov) extends uvm_env;

cip_base_vseq

This is the base virtual sequence class that will run on the cip virtual sequencer. This base class provides ‘sequencing’ set of tasks such as dut_init() and dut_shutdown() which are called within pre_start and post_start respectively. This sequence also provides an array of sub-sequences some of which are complete tests within themselves, but implemented as tasks. The reason for doing so is SystemVerilog does not support multi-inheritance so all sub-sequences that are identified as being common to all IP benches implemented as tasks in this base virtual sequence class. Some examples:

task run_csr_vseq_wrapper: This is a complete CSR test suite in itself - Extended IP CSR vseq can simply call this in the body. This is paired with a helper function add_csr_exclusions.
function add_csr_exclusions: This is extended in the IP CSR vseq to add exclusions when running the CSR suite of tests.
task tl_access: This is a common generic task to create a read or a write access over the TileLink host interface.
task cfg_interrupts, check_interrupts: All interrupt CSRs are standardized according to the comportability spec, which allows us to create common tasks to turn on / off interrupts as well as check them.
task run_tl_errors_vseq: This task will test all kinds of TileLink error cases, including unmapped address error, protocol error, memory access error etc. All the items sent in this task will trigger d_error and won't change the CSR/memory value.
task run_tl_intg_err_vseq: This task will test TLUL integrity error. It contains 2 parallel threads. The first one invokes the csr_rw seq to drive random, legal CSR accesses. The second drives a bad TLUL transaction that violates the payload integrity. The bad packet is created by corrupting upto 3 bits either in the integrity (ECC) fields (a_user.cmd_intg, a_user.d_intg), or in their corresponding command / data payload itself. The sequence then verifies that the DUT not only returns an error response (with d_error = 1), but also triggers a fatal alert and updates status CSRs such as ERR_CODE. The list of CSRs that are impacted by this alert event, maintained in cfg.tl_intg_alert_fields, are also checked for correctness.
task run_seq_with_rand_reset_vseq: This task runs 3 parallel threads, which are a sequence provided, run_tl_errors_vseq and reset sequence. After reset occurs, the other threads will be killed and then all the CSRs will be read for check. This task runs multiple iterations to ensure DUT won't be broken after reset and TL errors. To ensure the reset functionality works correctly, user will have to disable any internal reset from the stress_all sequence. Below is an example of disabling internal reset in hmac_stress_all_vseq.sv:
task run_same_csr_outstanding_vseq: This task tests the same CSR with non-blocking accesses as the regular CSR sequences don't cover that due to limitation of uvm_reg.

task run_mem_partial_access_vseq: This task tests the partial access to the memories by randomizing mask, size, and the 2 LSB bits of the address. It also runs with non-blocking access enabled.

// randomly trigger internal dut_init reset sequence
// disable any internal reset if used in stress_all_with_rand_reset vseq
if (do_dut_init) hmac_vseq.do_dut_init = $urandom_range(0, 1);
else hmac_vseq.do_dut_init = 0;

This class is type parameterized with the env cfg class type CFG_T, ral class type RAL_T and the virtual sequencer class type VIRTUAL_SEQUENCER_T so that the env cfg settings, the ral CSRs are accessible and the p_sequencer type can be declared.

class cip_base_vseq #(type RAL_T               = dv_base_reg_block,
                      type CFG_T               = cip_base_env_cfg,
                      type COV_T               = cip_base_env_cov,
                      type VIRTUAL_SEQUENCER_T = cip_base_virtual_sequencer) extends uvm_sequence;

All virtual sequences in the extended IP will eventually extend from this class and can hence, call these tasks and functions directly as needed.

cip_base_test

This basically creates the IP UVM env and its env cfg class instance. Any env cfg setting that may be required to be controlled externally via plusargs are looked up here, before the env instance is created. This also sets a few variables that pertain to how / when should the test exit on timeout or failure. In the run phase, the test calls run_seq which basically uses factory to create the virtual sequence instance using the UVM_TEST_SEQ string that is passed via plusarg. As a style guide, it is preferred to encapsulate a complete test within a virtual sequence and use the same UVM_TEST plusarg for all of the tests (which points to the extended IP test class), and only change the UVM_TEST_SEQ plusarg.

This class is type parameterized with the env cfg class type CFG_T and the env class type ENV_T so that when extended IP test class creates the env and env cfg specific to that IP.

class cip_base_test #(type CFG_T = cip_base_env_cfg,
                      type ENV_T = cip_base_env) extends uvm_test;

cip_tl_seq_item

This is extended class of tl_seq_item to generate correct integrity values in a_user and d_user.

Extending from CIP library classes

Let's say we are verifying an actual comportable IP uart which has uart_tx and uart_rx interface. User then develops the uart_agent to be able to talk to that interface. User invokes the ralgen tool to generate the uart_reg_block, and then starts developing UVM environment by extending from the CIP library classes in the following way.

uart_env_cfg

class uart_env_cfg extends cip_base_env_cfg #(.RAL_T(uart_reg_block));

User adds the uart_agent_cfg object as a member so that it remains as a part of the env cfg and can be accessed everywhere. In the base class's initialize() function call, an instance of uart_reg_block is created, not the dv_base_reg_block, since we override the RAL_T type.

uart_env_cov

class uart_env_cov extends cip_base_env_cov #(.CFG_T(uart_env_cfg));

User adds uart IP specific coverage items and uses the cov handle in scoreboard and test sequences to sample the coverage.

uart_virtual_sequencer

class uart_virtual_sequencer extends cip_base_virtual_sequencer #(.CFG_T(uart_env_cfg),
                                                                  .COV_T(uart_env_cov));

User adds the uart_sequencer handle to allow layered test sequences to send traffic to / from TileLink as well as uart interfaces.

uart_scoreboard

class uart_scoreboard extends cip_base_scoreboard #(.CFG_T(uart_env_cfg),
                                                    .RAL_T(uart_reg_block),
                                                    .COV_T(uart_env_cov));

User adds analysis ports to grab packets from the uart_monitor to perform end-to-end checking.

uart_env

class uart_env extends cip_base_env #(.CFG_T               (uart_env_cfg),
                                      .COV_T               (uart_env_cov),
                                      .VIRTUAL_SEQUENCER_T (uart_virtual_sequencer),
                                      .SCOREBOARD_T        (uart_scoreboard));

User creates uart_agent object in the env and use it to connect with the virtual sequencer and the scoreboard. User also uses the env cfg settings to manipulate the uart agent cfg settings if required.

uart_base_vseq

class uart_base_vseq extends cip_base_vseq #(.CFG_T               (uart_env_cfg),
                                             .RAL_T               (uart_reg_block),
                                             .COV_T               (uart_env_cov),
                                             .VIRTUAL_SEQUENCER_T (uart_virtual_sequencer));

User adds a base virtual sequence as a starting point and adds common tasks and functions to perform uart specific operations. User then extends from uart_base_vseq to add layered test sequences.

uart_base_test

class uart_base_test extends cip_base_test #(.ENV_T(uart_env), .CFG_T(uart_env_cfg));

User sets UVM_TEST plus arg to uart_base_test so that all tests create the UVM env that is automatically tailored to UART IP. Each test then sets the UVM_TEST_SEQ plusarg to run the specific test sequence, along with additional plusargs as required.

Configure Alert Device Agent from CIP library classes

To configure alert device agents in a block level testbench environment that is extended from this CIP library class, please follow the steps below:

${ip_name}_env_pkg.sv: Add parameter LIST_OF_ALERTS[] and NUM_ALERTS. Please make sure the alert names and order are correct. For example in otp_ctrl_env_pkg.sv:
```
parameter string LIST_OF_ALERTS[] = {"fatal_macro_error", "fatal_check_error"};
parameter uint NUM_ALERTS         = 2;
```
${ip_name}_env_cfg.sv: In function initialize(), assign LIST_OF_ALERTS parameter to list_of_alerts variable which is created in cip_base_env_cfg.sv. Note that this assignment should to be written before calling super.initialize(), so that creating alert host agents will take the updated list_of_alerts variable. For example in otp_ctrl_env_cfg.sv:
```
virtual function void initialize(bit [31:0] csr_base_addr = '1);
  list_of_alerts = otp_ctrl_env_pkg::LIST_OF_ALERTS;
  super.initialize(csr_base_addr);
```

tb.sv: Add DV_ALERT_IF_CONNECT macro that declares alert interfaces, connect alert interface wirings with DUT, and set alert_if to uvm_config_db. Then connect alert_rx/tx to the DUT ports. For example in otp_ctrl's tb.sv:

`DV_ALERT_IF_CONNECT()
otp_ctrl dut (
  .clk_i                      (clk        ),
  .rst_ni                     (rst_n      ),
  .alert_rx_i                 (alert_rx   ),
  .alert_tx_o                 (alert_tx   ),

Note that if the testbench is generated from uvmdvgen.py, using the -hr switch will automatically generate the skeleton code listed above for alert device agent. Details on how to use uvmdvgen.py please refer to the uvmdvgen document.

CIP Testbench

CIP testbench diagram The block diagram above shows the CIP testbench architecture, that puts together the static side tb which instantiates the dut, and the dynamic side, which is the UVM environment extended from CIP library. The diagram lists some common items that need to be instantiated in tb and set into uvm_config_db for the testbench to work.

Security Verification in cip_lib

CIP contains reusable security verification components, sequences and function coverage. This section describes the details of them and the steps to enable them.

Security Verification for bus integrity

The countermeasure of bus integrity can be fully verified via importing tl_access_tests and tl_device_access_types_testplan. The tl_intg_err test injects errors on control, data, or the ECC bits and verifies that the integrity error will trigger a fatal alert (provided via cfg.tl_intg_alert_name) and error status (provided via cfg.tl_intg_alert_fields) is set. Refer to section cip_base_env_cfg for more information on these 2 variables. The user may update these 2 variables as follows.

class ip_env_cfg extends cip_base_env_cfg #(.RAL_T(ip_reg_block));
  virtual function void initialize(bit [31:0] csr_base_addr = '1);
    super.initialize(csr_base_addr);
    tl_intg_alert_name = "fatal_fault_err";
    // csr / field name may vary in different IPs
    tl_intg_alert_fields[ral.fault_status.intg_err] = 1;

Security Verification for memory integrity

The memory integrity countermeasure stores the data integrity in the memory rather than generating the integrity on-the-fly during a read. The passthru_mem_intg_tests can fully verify this countermeasure. The details of the test sequences are described in the tl_device_access_types_testplan. Users need to override the task inject_intg_fault_in_passthru_mem to inject an integrity fault to the memory in the block common_vseq.

The following is an example from sram_ctrl, in which it flips up to MAX_TL_ECC_ERRORS bits of the data and generates a backdoor write to the memory.

class sram_ctrl_common_vseq extends sram_ctrl_base_vseq;
  ...
  virtual function void inject_intg_fault_in_passthru_mem(dv_base_mem mem,
                                                          bit [bus_params_pkg::BUS_AW-1:0] addr);
    bit[bus_params_pkg::BUS_DW-1:0] rdata;
    bit[tlul_pkg::DataIntgWidth+bus_params_pkg::BUS_DW-1:0] flip_bits;

    rdata = cfg.mem_bkdr_util_h.sram_encrypt_read32_integ(addr, cfg.scb.key, cfg.scb.nonce);

    `DV_CHECK_STD_RANDOMIZE_WITH_FATAL(flip_bits,
        $countones(flip_bits) inside {[1:cip_base_pkg::MAX_TL_ECC_ERRORS]};)

    `uvm_info(`gfn, $sformatf("Backdoor change mem (addr 0x%0h) value 0x%0h by flipping bits %0h",
                              addr, rdata, flip_bits), UVM_LOW)

    cfg.mem_bkdr_util_h.sram_encrypt_write32_integ(addr, rdata, cfg.scb.key, cfg.scb.nonce,
                                                   flip_bits);
  endfunction
endclass

Security Verification for shadow CSRs

The countermeasure of shadow CSRs can be fully verified via importing shadow_reg_errors_tests and shadow_reg_errors_testplan. The details of the test sequences are described in the testplan. Users need to assign the status CSR fields to cfg.shadow_update_err_status_fields and cfg.shadow_storage_err_status_fields for update error and storage error respectively.

class ip_env_cfg extends cip_base_env_cfg #(.RAL_T(ip_reg_block));
  virtual function void initialize(bit [31:0] csr_base_addr = '1);
    super.initialize(csr_base_addr);
    // csr / field name may vary in different IPs
    shadow_update_err_status_fields[ral.err_code.invalid_shadow_update] = 1;
    shadow_storage_err_status_fields[ral.fault_status.shadow] = 1;

Security Verification for REGWEN CSRs

If the REGWEN CSR meets the following criteria, it can be fully verified by the common csr_tests.

The REGWEN CSR and its related lockable CSRs are HW read-only registers.
The related lockable CSRs are not WO type, otherwise the read value is always 0 and CSR tests can't really verify if the write value is taken or not.
No CSR exclusions have been added to the REGWEN CSR and its related lockable CSRs. If not, users need to write a test to verify it separately since cip_lib and dv_base_reg can't predict its value. For example, the sram_ctrl_regwen_vseq has been added to verify ctrl_regwen and the the lockable register ctrl since ctrl is a WO register and excluded in CSR tests.

Functional coverage for REGWEN CSRs and their related lockable CSRs is generated automatically in dv_base_reg. The details of functional coverage is described in csr_testplan.

Security Verification for MUBI type CSRs

A functional covergroup of MUBI type CSR is automatically created in the RAL model for each MUBI CSR, which ensures True, False and at least N of other values (N = width of the MUBI type) have been collected. This covergroup won‘t be sampled in CSR tests, since CSR tests only test the correctness of the value of register read / write but it won’t check the block behavior when a different value is supplied to the MUBI CSR. Users should randomize the values of all the MUBI CSRs in non-CSR tests and check the design behaves correctly. The helper functions cip_base_pkg::get_rand_mubi4|8|12|16_val(t_weight, f_weight, other_weight) can be used to get the random values.

Security Verification for MUBI/LC_TX type ports

In OpenTitan Design Verification Methodology, it's mandatory to have 100% toggle coverage on all the ports. However, the MUBI defined values (True and False) are complement numbers. If users only test with True and False without using other values, toggle coverage can be 100%. Hence, user should add a functional covergroup for each MUBI type input port, via binding the interface cip_mubi_cov_if which contains a covergroup for MUBI. The type lc_ctrl_pkg::lc_tx_t is different than the Mubi4 type, as its defined values are different. So, it needs to be bound with the interface cip_lc_tx_cov_if. The helper functions cip_base_pkg::get_rand_mubi4|8|12|16_val(t_weight, f_weight, other_weight) and cip_base_pkg::get_rand_lc_tx_val can be used to get the random values.

The following is an example from sram_ctrl, in which it binds the coverage interface to 2 MUBI input ports.

module sram_ctrl_cov_bind;

  bind sram_ctrl cip_mubi_cov_if #(.Width(4)) u_hw_debug_en_mubi_cov_if (
    .rst_ni (rst_ni),
    .mubi   (lc_hw_debug_en_i)
  );

  bind sram_ctrl cip_lc_tx_cov_if u_lc_escalate_en_cov_if (
    .rst_ni (rst_ni),
    .val    (lc_escalate_en_i)
  );
endmodule

Note: The sim_tops in sim_cfg.hjson should be updated to include this bind file.

Security Verification for common countermeasure primitives

A security countermeasure verification framework is implemented in cip_lib to verify common countermeasure primitives in a semi-automated way.

Design Verification

cip_lib imports sec_cm_pkg, which automatically locates all the common countermeasure primitives and binds an interface to each of them. In the cib_base_vseq, it injects a fault to each of these primitives and verifies that the fault will lead to a fatal alert. The details of the sequences can be found in testplans - sec_cm_count_testplan, sec_cm_fsm_testplan and sec_cm_double_lfsr_testplan. If the block uses common security countermeasure primitives (prim_count, prim_sparse_fsm_flop, prim_double_lfsr), users can enable this sequence to fully verify them via following steps.

Import the applicable sec_cm testplans. If more checks or sequences are needed, add another testpoint in the block testplan. For example, when the fault is detected by countermeasure, some subsequent operations won’t be executed. Add a testpoint in the testplan to capture this sequence and the checks.
Import sec_cm_tests in sim_cfg.hjson file, as well as add applicable sec_cm bind files for sim_tops. The ip_sec_cm test will be added and all common countermeasure primitives will be verified in this test.

sim_tops: ["ip_ctrl_bind", "ip_ctrl_cov_bind",
           // only add the corresponding bind file if DUT has the primitive
           "sec_cm_prim_sparse_fsm_flop_bind",
           "sec_cm_prim_count_bind",
           "sec_cm_prim_double_lfsr_bind"]

Import sec_cm_pkg in the env_pkg

package ip_env_pkg;
  import uvm_pkg::*;
  import sec_cm_pkg::*;
  …

Set alert name for countermeasure if the alert name is different from the default name - “fatal_fault”.

class ip_env_cfg extends cip_base_env_cfg #(.RAL_T(ip_reg_block));
  virtual function void initialize(bit [31:0] csr_base_addr = '1);
    super.initialize(csr_base_addr);
    sec_cm_alert_name = "fatal_check_error";

Override the check_sec_cm_fi_resp task in ip_common_vseq to add additional sequences and checks after fault injection. This is an example from keymgr, in which CSR fault_status will be updated according to the location of the fault and the operation after fault inject will lead design to enter StInvalid state.

class keymgr_common_vseq extends keymgr_base_vseq;
  virtual task check_sec_cm_fi_resp(sec_cm_base_if_proxy if_proxy);
    bit[TL_DW-1:0] exp;

    super.check_sec_cm_fi_resp(if_proxy);

    case (if_proxy.sec_cm_type)
      SecCmPrimCount: begin
        // more than one prim_count are used, distinguishing them through the path of the primitive.
        if (!uvm_re_match("*.u_reseed_ctrl*", if_proxy.path)) begin
          exp[keymgr_pkg::FaultReseedCnt] = 1;
        end else begin
          exp[keymgr_pkg::FaultCtrlCnt] = 1;
        end
      end
      SecCmPrimSparseFsmFlop: begin
        exp[keymgr_pkg::FaultCtrlFsm] = 1;
      end
      default: `uvm_fatal(`gfn, $sformatf("unexpected sec_cm_type %s", if_proxy.sec_cm_type.name))
    endcase
    csr_rd_check(.ptr(ral.fault_status), .compare_value(exp));

    // after an advance, keymgr should enter StInvalid
    keymgr_advance();
    csr_rd_check(.ptr(ral.op_status), .compare_value(keymgr_pkg::OpDoneFail));
    csr_rd_check(.ptr(ral.working_state), .compare_value(keymgr_pkg::StInvalid));
  endtask : check_sec_cm_fi_resp

Fault injection may trigger unexpected SVA errors. Override the sec_cm_fi_ctrl_svas function to disable them. sec_cm_fi_ctrl_svas(.enable(1)) will be invoked before injecting fault. After reset, sec_cm_fi_ctrl_svas(.enable(0)) will be called to re-enable the SVA checks.

class keymgr_common_vseq extends keymgr_base_vseq;
   virtual function void sec_cm_fi_ctrl_svas(sec_cm_base_if_proxy if_proxy, bit enable);
    case (if_proxy.sec_cm_type)
      SecCmPrimCount: begin
        if (enable) begin
          $asserton(0, "tb.keymgr_kmac_intf");
          $asserton(0, "tb.dut.tlul_assert_device.gen_device.dDataKnown_A");
          $asserton(0, "tb.dut.u_ctrl.DataEn_A");
          $asserton(0, "tb.dut.u_ctrl.DataEnDis_A");
          $asserton(0, "tb.dut.u_ctrl.CntZero_A");
          $asserton(0, "tb.dut.u_kmac_if.LastStrb_A");
          $asserton(0, "tb.dut.KmacDataKnownO_A");
        end else begin
          $assertoff(0, "tb.keymgr_kmac_intf");
          $assertoff(0, "tb.dut.tlul_assert_device.gen_device.dDataKnown_A");
          $assertoff(0, "tb.dut.u_ctrl.DataEn_A");
          $assertoff(0, "tb.dut.u_ctrl.DataEnDis_A");
          $assertoff(0, "tb.dut.u_ctrl.CntZero_A");
          $assertoff(0, "tb.dut.u_kmac_if.LastStrb_A");
          $assertoff(0, "tb.dut.KmacDataKnownO_A");
        end
      end
      SecCmPrimSparseFsmFlop: begin
        // No need to disable any assertion
      end

      default: `uvm_fatal(`gfn, $sformatf("unexpected sec_cm_type %s", if_proxy.sec_cm_type.name))
    endcase
  endfunction: sec_cm_fi_ctrl_svas

Formal Verification

Please refer to formal document on how to create a FPV environment for common countermeasures.