[entropy_src] V1 Signoff

[msfschaffner]

Description

Ensure V1 signoff criteria are fulfilled after focus area changes have landed.

[johngt]

@vogelpi / @h-filali - as an observer it looks like there have been quite a few changes so DV effort might be under-represented here now. Please update as appropriate.

[vogelpi]

Commits since Earlgrey-ES tapeout

git rev-parse --short HEAD
a47ab77

git log Earlgrey-M2.5.2-RC0..HEAD --oneline hw/ip/entropy_src
54661e6 [entropy_src] Reduce depth of Observe FIFO
2d82cc8 [entropy_src] Rework the swread packer FIFO to reduce area
fcd7af1 [entropy_src] Reduce depth of esfinal FIFO from 4 to 3 entries
-> changes to reduce area for M2
4e422bd [entropy_src/dv] Test whether noise source symbols are not dropped

2b8870c [entropy_src] Align enable delay module with fixed CS AES Halt interface
534a41e [entropy_src] Remove unneeded main SM state and input signals
0b88a66 [entropy_src/dv] Reduce max delay for CS AES Halt IF in max rate test
-> related to fixing the CS AES halt request interface

74a6e9b [entropy_src] Add FIFO to deal with backpressure from the conditioner
-> required for FIPS compliance
c2c27db [entropy_src] Align prim_fifo_sync instantiation parameters
-> Improving security
7ebb11a [entropy_src] Fix FIFO controls, move drop point to before postht FIFO
-> required for FIPS compliance
f76a236 [entropy_src] Fix a Verilator lint warning

21adde1 [entropy_src] Fix CS AES Halt interface
15f75fa [kmac, sha3] Add REQ/ACK interface to delay Keccak operations
01b73a0 [entropy_src/dv] Fix usage of rng_max_delay plusarg
2b9338d [entropy_src/dv] Fix CS AES Halt agent configuration
-> helps saving power, required to properly assess conditioner back pressure, relevant for FIPS compliance

043b0e0 [kmac] Simplify randomness update requests and PRNG control logic
-> not related to ENTROPY_SRC
e0a5f9d [entropy_src] Remove line diabling TRNG when esrng FIFO is full
-> required for FIPS compliance
3eadcfd [entropy_src/rtl] Change the mubi4 true test to loose
03afa4c [entropy_src/rtl] Keep applying fw_ov_rd_fifo_overflow instead of pulsing
-> bug fixs

381ccf9 [entropy_src/rtl] Move the esbit FIFO down in sv file
ea70f00 [entropy_src/doc] Move the esbit packer FIFO in the block diagram
0b25451 [entropy_src/doc] Align the documentation with the moved esbit FIFO
c35040f [entropy_src/dv] Adapt the scoreboard to the repositioned esbit FIFO
46fe194 [entropy_src/rtl] Move back 1-4 packer
-> for de-risking FIPS certification

29866cc [entropy_src/doc] Adapt documentation to the new CONF register changes
03298b5 [entropy_src/dv] Add coverage for the new CONF changes
b3b4207 [entropy_src/dv] Align DV with new fips_flag changes
6b5f40f [entropy_src/rtl] Use the new fips_flag registers
55763e1 [entropy_src/rtl] Add new fips fields to CONF register
-> for de-risking FIPS certification, enable OTBN operating in firmware override: extract and insert mode

0528bc2 [entropy_src/doc] Document how to use fw_ov mode with bypass
0604938 [entropy_src/dv] Fix a failing rng_vseq test
fae3235 [dv/csr_utils] Change csr_peek to return the peeked value
79be09f [entropy_src/doc] Document operation upon health tests failures
809ba9c [entropy_src/doc] Document behavior of SHA3 conditioner engine

3f447cc [otp_ctrl] Remove entropy_src chicken switches
-> these switches need to remain enabled in PROD to enable KAT of the conditioner and the firmware override modes

c721c51 [rtl, prim] Add 'commit' functionality to prim_count
61a237e [util/reggen] reverse order of substruct generation
-> not specifically related to ENTROPY_SRC

e0a3193 [doc] Clearly expand PTRNG acronym in entropy_src

de31bdf [reggen] Remove the devmode input
963a500 [doc] Minor tweak to md sanitisation code
-> not specifically related to ENTROPY_SRC

b0fb96a [es/dv] Add test_es_health_test_failed task to intr vseq
316431f [es/dv] Get intr vseq working again
50ecc02 [es/dv] Add interrupt test
f192e3e [es/dv] Add interrupt checks to the error vseq
975a6eb [adc_ctrl,dv] Tidy up access to intr_state in env_cfg files
a5a80a6 [chip-test] List ENTROPY_SRC functional features
d940eaa [doc] Add extra links to registers and fields for entropy_src
d3326c1 [doc] Fix entropy_src links to renamed registers
1b16ca2 [reggen] Add mubi support SWAccess that sets/clears a reg

59f8142 [doc] Moved badges over to using hosted images
-> not specifically related to ENTROPY_SRC

7688e71 [reggen] Add initial support for version and cip_id hjson fields
fbd888e Revert "[reggen] Add CIP_IDs and bump all major versions"
9b974b1 [doc] entropy_src registers now using CMDGEN
0ba10b3 [reggen] Add CIP_IDs and bump all major versions

Issues closed since the Earlgrey-ES tapeout

• [entropy_complex] Corner case tests at the chip level #10970
  Chip-level test / SiVal issue, it got decided that this better tested on the chip.
• [entropy_src] FIPS non-compliance with RNG bit select #11207
  RTL change implemented and DV aligned with [entropy_src/rtl] Move the 1-4 esbit packer #21626
• [chip-test] chip_sw_entropy_src_fuse_en_fw_read #13229
  Chip-level test / SiVal issue, got removed with [otp_ctrl] Remove entropy_src chicken switches #21118.
• [csrng] Future improvement for reseed blocking #14505
  Closed as not planned.
• [entropy_src/dv] Use the internal reset monitor to know a mid-test reset occurred #14649
  Closed as not planned.
• [dv/cdc] Enable CDC instrumentation in all ips #16689
  Not specifically ENTROPY_SRC related.
• [entropy_src] SHA3 core / Keccak active without CS AES Halt #17941
  RTL change implemented and DV aligned with [entropy_src, sha3] Fix CS AES Halt interface and entropy_src_rng_max_rate test #21787
• [entropy_src/dv] Verify that entropy stops propagating when an alert is raised #18889
  DV
• [entropy_src/dv] Find out what happened to the group coverage #20565
  DV, fixed, it turned out the project was using a single deterministic seed for all simulations for some time.
• [entropy_src] Restarting physical noise source through rng_en #20947
  RTL change implemented and DV aligned with [entropy_src] Remove line diabling TRNG when esrng FIFO is full #21685, a second PR [entropy_src] Fix handling of backpressure in the hardware pipeline #21799 was needed to fix the back pressure for good. Some DV / SW items remain. This is tracked as part of [entropy_src] Backpressure handling follow-up work #21855.
• [entropy_src, OTBN] Consider renaming or removing the FIPS signal #20949
  RTL change implemented and DV aligned with [entropy_src/rtl] Make the fips bit sw configurable #21369.
• [entropy_src] Test FIPS compatibility of FW override / bypass mode #20952
  SiVal tests implemented with [entropy_src,testplan] Add testpoints for firmware override mode #21150 and [sival] Add test for the entropy source's firmware extract and insert mode #21562
• [entropy_src] Make sure unaltered raw data can be extracted for FIPS randomness validation #20953
  DV task taken care of with [entropy_src/dv] Test whether noise source symbols are not dropped #21821
• [entropy_src] Make HW health tests configurable to process either 1 or 4 bit samples/symbols #20954
  Replacement issue for [entropy_src] FIPS non-compliance with RNG bit select #11207, RTL change implemented and DV aligned with [entropy_src/rtl] Move the 1-4 esbit packer #21626
• [entropy_src] Fix Observe FIFO overflow bit #21279
  Bug fixed with [entropy_src/rtl] Fix observe fifo overflow reg #21640
• [chip-test] chip_sw_entropy_src_ast_rng_req #21390
  SiVal
• [chip-test] chip_sw_entropy_src_csrng #21391
  Sival
• [chip-test] chip_sw_entropy_src_known_answer_tests #21392
  SiVal
• [chip-test] chip_sw_entropy_src_bypass_mode_health_tests #21393
  SiVal
• [chip-test] chip_sw_entropy_src_validation #21395
  SiVal
• [entropy_src] Outline potential hardware changes for ECDSA sigverify in ROM #21652
  Closed as not planned
• [entropy_src] Determine when and what FIFOs can drop entropy #21686
  Closed with [entropy_src] Fix handling of backpressure in the hardware pipeline #21799

Currently open issues

• [entropy_src] Statistical Arguments on entropy_src health check definitions #2111
  ROM_EXT
• Error status registers during an operation, and otherwise #7901
  Not specific to ENTROPY_SRC, recommendation is to formulate guidance for future designs, tracked in [doc] Potential additions to comportability definition and specification #20680
• [hw/csrng] Integrity protection for KV in CSRNG #10738
  Entropy complex issue, future release
• [cryptolib] entropy driver #14363
  Cryptolib
• [cryptolib] continuous mode config incl. health checks for entropy_src #14364
  Cryptolib
• [entropy_src] Power Management Improvements #14417
  Options for power saving, related to [entropy_src] Power management functionality and tests #22293 and [ast, entropy_src] Reducing idle power #22223.
• [entropy_src/dv] Complete extht verification  #16276
  DV, not relevant for Prod as Earlgrey doesn't implement external health tests
• [chip-test] Move C tests without external host from tests/sim_dv/ to tests/ #16636
  Not relevant for ENTROPY_SRC anymore. The corresponding test got removed with [otp_ctrl] Remove entropy_src chicken switches #21118.
• [top_darjeeling] RNG integration #17109
  Not relevant for Earlgrey, Darjeeling only.
• [entropy_src/dv] Verify no entropy dropped incorrectly in Firmware Override - Extract & Insert mode #18109
  Tracked as part of D3 / M4.
• [rom_ext] Check entropy configuration in ROM_EXT #18649
  ROM_ext
• [entropy_src/dv] Health tests sometimes fail in scoreboard but not in DUT #18797
  Tracked as part of V3 / M5.
• [entropy_src/dv] Randomize and constrain additional values in DV env config #18836
  Tracked as part of V3 / M5.
• [entropy_src/dv] Verify firmware override write and read FIFO over-/underflows #18837
  Tracked as part of V3 / M5.
• [entropy_src/dv] Verify rng_fips_o #18842
  Tracked as part of V3 / M5, but can likely be closed now.
• [crypto] Determine appropriate thresholds for entropy health tests. #19392
  Cryptolib, duplicate of [entropy_src] Statistical Arguments on entropy_src health check definitions #2111
• [sival] prod_all_tests #20194
  SiVal, Not specific to ENTROPY_SRC
• [entropy_src] Documenting failure/error behavior #20948
  Addressed by [entropy_src] Improve documentation #22324
• [chip-test] chip_sw_entropy_src_fips_mode_health_tests #21394
  SiVal
• [entropy_src] Backpressure handling follow-up work #21855
  Follow-up DV and software work, tracked as part of M4
• [entropy_src] Functional coverage metrics dropped #21888
  Tracked as part of V2(S) / M4.
• [top_earlgrey] Area optimizations for production #22025
  Not ENTROPY_SRC specific
• [ast, entropy_src] Reducing idle power #22223, [prodc-integration] Normal Sleep Power Consumption High #22241 and [entropy_src] Power management functionality and tests #22293
  Power saving discussions
• [entropy_src] Need support for testing health tests #22289
  RTL feature request
• [entropy_src] software poll mode operations #22295
  Integration question, mostly covered by currently available documentation.
• [entropy_src] measurement of entropy is needed to configure health checks #22320
  Duplicate of [entropy_src] Statistical Arguments on entropy_src health check definitions #2111 and [crypto] Determine appropriate thresholds for entropy health tests. #19392.
• [entropy_src, ROM] conditioning function shall be accessible for known-answer test and tested before use #22323
  RTL and chip-level test items covered, ROM_ext part open
• [entropy_src/dv] Extend entropy_src_err_vseq to test hardened FIFO pointers #22326
  Verification of hardened prim_fifo_sync primitives as part of V2S / M4.

Coverage report from 29/03/2024

Summary

As part of M2, the following main RTL changes have been done. Unless stated below, DV and documentation have been updated inline with the RTL change:

• Moving the 1-to-4 esbit packer to after the health tests [entropy_src/rtl] Move the 1-4 esbit packer #21626
• Fixing the CS AES halt request interface [entropy_src, sha3] Fix CS AES Halt interface and entropy_src_rng_max_rate test #21787
• Avoiding internal back pressure shutting down the PTRNG noise source [entropy_src] Remove line diabling TRNG when esrng FIFO is full #21685 and [entropy_src] Fix handling of backpressure in the hardware pipeline #21799
  • Documentation alignment in outstanding PR [entropy_src] Improve documentation #22324.
  • Remaining DV / SW work is tracked as in [entropy_src] Backpressure handling follow-up work #21855 as part of V2(S) / M4.
• Making the FIPS bit and rng_fips_o signals software defined [entropy_src/rtl] Make the fips bit sw configurable #21369

Some of these changes break API compatibility , thus the version needs to be increased which is happening with this outstanding PR #22327

Despite pushing hard to keep the DV aligned with the RTL to not break things (and doing really a great job @h-filali ) we unfortunately don't meet the coverage metrics anymore to sign of at V2(S) again. Pass rates are still really good (all tests above 94%) but the coverage dropped. The reason for the coverage drop is twofold:

1. There were quite some RTL changes and we should simply update the coverage exclusion files (and review them of course!)
2. Due to adding new configuration bits in [entropy_src/rtl] Make the fips bit sw configurable #21369 and adding coverage for them plus crosses without incrasing the number of seeds, functional coverage now dropped from above 90% to roughly 57.5%. We need to have a conversation what makes sense here.

Both these things are tracked in #21888.

My suggestion is to sign ENTROPY_SRC v.2.0.0 off at V1.

@andreaskurth , @h-filali , please let me know what you think.

[andreaskurth]

Signing entropy_src off at V1 SGTM. Thx for the detailed signoff analysis, @vogelpi! 👍