_k_r2_001b2c_gate.nx

_k_r2_001b2c_gate.nx -- the K-R2-001b2c gate (virtio-MMIO STATUS-BYTE WRITEBACK layer; the fourth slice of the K-R2-001b virtqueue epic, on top of b2b's avail-consume + used-ring writeback). Drives the full author->handshake->queue-config->descriptor-DMA->avail/used-> status-byte chain with NO mocks: runs the REAL nx_virtio_hs_emit (the team AUTHORS the rv64 image + the TABLE-COMPUTED golden transcript from the status spec), then RUNS the image on the SOVEREIGN rv64 emulator (rv64im_min_sim + the rv64im_min_virtio device now, on the b2b QueueNotify kick, after the used-ring writeback, DMA-WRITING the virtio-blk request status byte VIRTIO_BLK_S_OK=0 into the status descriptor's guest buffer + latching it into the QueueStatPeek RO register -- the PRIMARY, gating lane: Nishi owns the runtime) and asserts the captured serial transcript CONTAINS the emitter's golden ("VIO ACK DRV FEAT OK VQ DESC USED STAT\n" -- after the used-ring writeback the device wrote the OK status byte, the driver READ QueueStatPeek BACK and verified it == stat_expected: the status-byte writeback binding proof) AND the sovereign emu reports a clean SiFive-finisher halt. Then the ALIGNMENT lane: qemu-system-riscv64 -machine virt -global virtio-mmio.force-legacy=true with a REAL virtio-blk-device backing. The gate authors a SECOND image from a base-rewritten spec (the blk device lands at slot 0x10008000) and runs the SAME driver against the REAL legacy virtio-blk transport: it completes the handshake + queue config, lays the SAME descriptor + the SAME avail ring into qemu guest RAM, and kicks the real QueueNotify -- the real legacy transport genuinely walks the ring. The sovereign- only QueueDescPeek / QueueUsedIdxPeek / QueueStatPeek result registers are model instruments the real device does not expose (they read 0), so on qemu the descriptor-DMA + used-ring + status-byte verifies gracefully drop " DESC" / " USED" / " STAT"; the gate asserts the qemu transcript contains the b1 prefix golden ("VIO ACK DRV FEAT OK VQ") -- proving the SAME driver lays the avail ring + kicks the real device -> lanes AGREE on every register the real transport can observe. Finally a TAMPER test: corrupt the QueueStatPeek-EXPECTED constant in the sovereign image (the driver loads its own QueueStatPeek read-back into t3 via lwu and compares against this li-loaded expected in t4; bumping the expected's immediate makes t3 != t4) -> the read-back verify branches PAST stage 8 straight to the finisher -> the transcript loses ONLY its " STAT" canary (the "VIO ACK DRV FEAT OK VQ DESC USED" tail survives) -> the gate MUST go RED. Evidence -> knowledge/status/virtio_blk.log (STATGATE row; the queue row's ||MARK= reads it). Sovereign orchestration (fork/dup3/execve/wait4). license_tier: ORIGINAL