Robert Allan JamesandClaude Opus 5.5
acea36ea55
- Investigation (riscv64): completions are slow, not lost -- up to 15 ms, while the ~1M-iteration bound was ~14 ms of guest time. Each timeout left the request in the device while the driver forgot it; the next request took its used entry as its own and returned before its own I/O finished, and so did every later one (394 in one boot), rewriting descriptors the device was still reading. - Fix: VBLK_TIMEOUT_MS (2 s) on the raw hardware counter; each request waits for exactly one more used entry; a timed-out request stays outstanding and its completion is drained before anything is reused, or the next request is refused untouched. Counters for timeouts, late drains and busy refusals. - After the fix, all three ISAs: 0 timeouts, 0 unaccounted completions over 1,912 I/Os; riscv64 slowest completion 7.7 ms (was 15.1). - Standard sequence on amd64/aarch64/riscv64: hash, G, ledger unchanged; 0 timeouts in the riscv64 log. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
65 lines
2.2 KiB
C
65 lines
2.2 KiB
C
/*
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* virtio_blk.h — Virtio 1.0 block device driver for StarKernel
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*
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* Presents a blkio_dev_t interface for attachment to the StarForth
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* block subsystem via blk_subsys_attach_device().
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*
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* Only one virtio-blk device is supported (the Artemis disk).
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* I/O is synchronous (polling) — no interrupts, no DMA descriptors
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* beyond the split virtqueue shared memory.
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*
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* Artemis disk identification heuristic:
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* The Artemis disk image is 30 MB (61440 sectors). The first virtio-blk
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* device matching PCI vendor=0x1AF4 / device=0x1042 or 0x1001 whose
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* sector count equals 61440 is selected. If no exact match, the first
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* device found is used.
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*/
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#ifndef STARKERNEL_VIRTIO_BLK_H
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#define STARKERNEL_VIRTIO_BLK_H
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#include <stdint.h>
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#include "blkio.h"
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/* StarForth block size and sector ratio */
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#define VBLK_SECTOR_SIZE 512u
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#define VBLK_SECTORS_PER_BLOK 2u /* 1 KiB Forth block = 2 × 512-byte sectors */
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#define VBLK_ARTEMIS_SECTORS 61440u /* 30 MB */
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/* virtio PCI vendor */
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#define VIRTIO_PCI_VENDOR_ID 0x1AF4u
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/* device IDs */
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#define VIRTIO_BLK_DEVICE_MODERN 0x1042u
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#define VIRTIO_BLK_DEVICE_LEGACY 0x1001u
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/* virtio-blk request types */
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#define VIRTIO_BLK_T_IN 0u
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#define VIRTIO_BLK_T_OUT 1u
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/* virtio-blk status codes (device → driver) */
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#define VIRTIO_BLK_S_OK 0u
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#define VIRTIO_BLK_S_IOERR 1u
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#define VIRTIO_BLK_S_UNSUPP 2u
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/*
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* virtio_blk_find_artemis — locate the Artemis virtio-blk disk, initialise
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* the driver, and fill in *dev_out so the caller
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* can pass it to blk_subsys_attach_device().
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*
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* dev_out must point to a zero-initialised blkio_dev_t.
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*
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* Returns 0 on success.
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* Returns -1 if no virtio-blk device was found on the PCI bus.
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* Returns -2 on driver initialisation failure (bad BAR, queue setup, etc.).
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*/
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int virtio_blk_find_artemis(blkio_dev_t *dev_out);
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/* FABRIC-3.10.8 K-6 counters: requests that timed out (left outstanding),
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* late completions drained before a later request, and requests refused
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* because an earlier one was still in the device. */
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uint64_t virtio_blk_timeouts(void);
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uint64_t virtio_blk_late_consumed(void);
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uint64_t virtio_blk_refused_busy(void);
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#endif /* STARKERNEL_VIRTIO_BLK_H */
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