Months ago, I had issues with the AHCI driver not working with part_blk. I tested a simple scenario with AHCI and a non-writing version of test-blk-cli. It didn't work (test-blk-cli-nowrite didn't give any output), but the AHCI driver gave its normal output. I tested a slightly modified config using rom_blk instead of ahci, and it worked just fine. Any ideas about what might be wrong?