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/* virtio_blk.c — UTSM virtio-blk 设备模拟后端。
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*
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* 为 Linux guest 提供 virtio-blk 块设备。guest 的块读写请求经
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* virtqueue 传入，本后端桥接到 UTSM 真实块设备（block API，AHCI/SATA）。
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*
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* Virtio Spec 1.1 §5.2 (Block Device)。
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* 请求描述符链： [header(16B, R)] [data(N*512B, R/W)] [status(1B, W)]
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* 支持的操作：VIRTIO_BLK_T_IN(读)、VIRTIO_BLK_T_OUT(写)、VIRTIO_BLK_T_GET_ID。
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*
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* 设计说明：
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* - 桥接到 UTSM block API 的第 0 个设备（ahci0 SATA 盘）。
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* - guest 把 Arch rootfs 镜像当作 /dev/vda 挂载；镜像需预先写入 SATA 盘
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* 的某个分区/LBA 区间（由 mkfat32/build 流程或独立 raw 区提供）。
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* - 当前为最小可用：扇区 512B，单队列，无 flush/discard。
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*/
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#include <utsm/virtio_mmio.h>
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#include <utsm/linux_loader.h>
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#include <utsm/block.h>
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#include <utsm/log.h>
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#include <utsm/types.h>
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/* virtio-blk 请求头（Virtio Spec 1.1 §5.2.6.2） */
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struct virtio_blk_outhdr {
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u32 type; /* VIRTIO_BLK_T_* */
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u32 reserved; /* (ioprio) */
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u64 sector; /* 起始扇区（512B 单位） */
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} __attribute__((packed));
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#define VIRTIO_BLK_T_IN 0 /* 读 */
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#define VIRTIO_BLK_T_OUT 1 /* 写 */
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#define VIRTIO_BLK_T_FLUSH 4
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#define VIRTIO_BLK_T_GET_ID 8
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#define VIRTIO_BLK_S_OK 0
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#define VIRTIO_BLK_S_IOERR 1
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#define VIRTIO_BLK_S_UNSUPP 2
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/* feature bits */
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#define VIRTIO_BLK_F_SIZE_MAX 1
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#define VIRTIO_BLK_F_SEG_MAX 2
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#define VIRTIO_BLK_F_BLK_SIZE 6
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#define VIRTIO_BLK_F_FLUSH 9
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/* device config 空间（VIRTIO_MMIO_CONFIG 起） */
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struct virtio_blk_config {
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u64 capacity; /* 总扇区数（512B） */
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u32 size_max;
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u32 seg_max;
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u16 geometry[4];
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u32 blk_size;
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/* ... 其余字段省略 */
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} __attribute__((packed));
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/* 后端状态 */
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static u64 g_blk_capacity; /* 扇区数 */
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static u32 g_blk_sector_size = 512;
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static int g_blk_bound = -1; /* 绑定的 UTSM block 设备索引 */
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/* 读取 device config 空间 */
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static u32 blk_read_config(u32 offset, int width) {
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(void)width;
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struct virtio_blk_config cfg;
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/* 填零后逐字段读取 */
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u8 *c = (u8 *)&cfg;
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for (u32 i = 0; i < sizeof(cfg); i++) c[i] = 0;
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cfg.capacity = g_blk_capacity;
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cfg.size_max = 128; /* 单请求最大 128 扇区 */
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cfg.seg_max = 32;
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cfg.blk_size = g_blk_sector_size;
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/* 按 offset 返回 32 位窗口 */
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if (offset + 4 <= sizeof(cfg)) {
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u32 v;
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u8 *src = (u8 *)&cfg + offset;
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v = (u32)src[0] | ((u32)src[1] << 8) | ((u32)src[2] << 16) | ((u32)src[3] << 24);
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return v;
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}
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return 0;
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}
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/* 处理一个块请求描述符链。返回写入 guest 的字节数（用于 used.len）。 */
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static u32 blk_handle_chain(struct virtq_desc *desc, u16 head, u32 qnum) {
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(void)qnum;
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if (!desc) return 0;
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/* 第一个描述符：请求头（driver→device，16 字节） */
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struct virtio_blk_outhdr *hdr =
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(struct virtio_blk_outhdr *)virtio_gpa_to_host(desc[head].addr);
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if (!hdr) return 0;
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u32 type = hdr->type;
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u64 sector = hdr->sector;
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/* 沿描述符链找到 data 与 status 描述符 */
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u16 cur = head;
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u16 data_idx = 0xFFFF, status_idx = 0xFFFF;
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int hops = 0;
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if (desc[cur].flags & VIRTQ_DESC_F_NEXT) {
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data_idx = desc[cur].next;
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cur = data_idx;
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/* data 之后可能还有 status */
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while ((desc[cur].flags & VIRTQ_DESC_F_NEXT) && hops < 16) {
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cur = desc[cur].next;
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hops++;
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}
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/* 最后一个是 status（device write，1 字节） */
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status_idx = cur;
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}
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u8 *status = (u8 *)0;
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if (status_idx != 0xFFFF && (desc[status_idx].flags & VIRTQ_DESC_F_WRITE)) {
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status = (u8 *)virtio_gpa_to_host(desc[status_idx].addr);
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}
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u32 bytes_done = 0;
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u8 result = VIRTIO_BLK_S_OK;
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const dkm_block_api *blk = block_get_api();
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switch (type) {
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case VIRTIO_BLK_T_IN: { /* 读：块设备 → guest data buffer */
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if (data_idx == 0xFFFF || g_blk_bound < 0 || !blk) {
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result = VIRTIO_BLK_S_IOERR;
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break;
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}
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u8 *dbuf = (u8 *)virtio_gpa_to_host(desc[data_idx].addr);
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u32 dlen = desc[data_idx].len;
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if (!dbuf) { result = VIRTIO_BLK_S_IOERR; break; }
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u32 nsec = dlen / 512;
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if (nsec == 0) nsec = 1;
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if (blk->read((u32)g_blk_bound, sector, nsec, dbuf) != 0) {
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result = VIRTIO_BLK_S_IOERR;
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} else {
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bytes_done = dlen;
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}
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break;
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}
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case VIRTIO_BLK_T_OUT: { /* 写：guest data buffer → 块设备 */
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if (data_idx == 0xFFFF || g_blk_bound < 0 || !blk) {
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result = VIRTIO_BLK_S_IOERR;
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break;
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}
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const u8 *dbuf = (const u8 *)virtio_gpa_to_host(desc[data_idx].addr);
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u32 dlen = desc[data_idx].len;
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if (!dbuf) { result = VIRTIO_BLK_S_IOERR; break; }
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u32 nsec = dlen / 512;
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if (nsec == 0) nsec = 1;
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if (blk->write((u32)g_blk_bound, sector, nsec, dbuf) != 0) {
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result = VIRTIO_BLK_S_IOERR;
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} else {
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bytes_done = 0; /* 写操作 used.len=0 */
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}
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break;
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}
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case VIRTIO_BLK_T_GET_ID: {
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if (data_idx != 0xFFFF) {
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char *idbuf = (char *)virtio_gpa_to_host(desc[data_idx].addr);
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if (idbuf) {
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const char *id = "DESHAB-VIRTIO-BLK";
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u32 i = 0;
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for (; id[i] && i < desc[data_idx].len - 1; i++) idbuf[i] = id[i];
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idbuf[i] = 0;
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bytes_done = i + 1;
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}
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}
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break;
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}
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case VIRTIO_BLK_T_FLUSH:
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result = VIRTIO_BLK_S_OK; /* 无写缓存，直接成功 */
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break;
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default:
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result = VIRTIO_BLK_S_UNSUPP;
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break;
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}
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/* 写状态字节 */
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if (status) *status = result;
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return bytes_done;
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}
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/* queue_notify：guest 提交了块请求，处理队列。 */
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static u16 g_blk_last_avail;
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static void blk_queue_notify(u32 queue_idx) {
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struct virtq_desc *desc;
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struct virtq_avail *avail;
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struct virtq_used *used;
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u32 qnum;
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if (virtio_queue_get_ptrs(VIRTIO_ID_BLOCK, queue_idx,
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&desc, &avail, &used, &qnum) != 0) {
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return;
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}
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/* 处理自上次以来的所有新 avail 请求 */
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u16 cur = g_blk_last_avail;
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u16 used_idx = used->idx;
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while (cur != avail->idx) {
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u16 head = avail->ring[cur % qnum];
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u32 len = blk_handle_chain(desc, head, qnum);
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/* 写 used 回执 */
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used->ring[used_idx % qnum].id = head;
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used->ring[used_idx % qnum].len = len;
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used_idx++;
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cur++;
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}
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virtio_queue_bump_used(used, used_idx);
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g_blk_last_avail = cur;
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}
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static void blk_reset(void) {
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g_blk_last_avail = 0;
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}
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/* 后端结构体 */
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static struct virtio_backend g_blk_backend = {
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.device_id = VIRTIO_ID_BLOCK,
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.gpa_base = VIRTIO_MMIO_BLK_GPA,
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.irq = 5, /* guest ISA IRQ5（cmdline :5，vector 0x35） */
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.num_queues = 1,
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.queue_size = 128,
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.device_features = (1ULL << VIRTIO_F_VERSION_1) |
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(1ULL << VIRTIO_BLK_F_SIZE_MAX) |
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(1ULL << VIRTIO_BLK_F_SEG_MAX) |
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(1ULL << VIRTIO_BLK_F_BLK_SIZE) |
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(1ULL << VIRTIO_BLK_F_FLUSH),
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.config_len = sizeof(struct virtio_blk_config),
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.read_config = blk_read_config,
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.queue_notify = blk_queue_notify,
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.reset = blk_reset,
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};
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void virtio_blk_backend_init(void) {
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/* 绑定 UTSM 第 0 个块设备（ahci0 SATA 盘）作为后端存储 */
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const dkm_block_api *blk = block_get_api();
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if (blk && blk->device_count() > 0) {
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g_blk_bound = 0;
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u64 ssize = blk->sector_size(0);
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if (ssize > 0) g_blk_sector_size = (u32)ssize;
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/* 从设备名推算容量不可得，用默认值（guest 端可再探测）。
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* 实际 capacity 需读 ATA IDENTIFY；这里给 4GB 占位，
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* guest mkfs/mount 会按此上限工作。 */
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g_blk_capacity = 8ULL * 1024 * 1024 * 1024 / 512; /* 8GB in sectors */
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log_info("[VBLK] bound to UTSM block device 0");
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log_hex64("[VBLK] capacity(sectors)=", g_blk_capacity);
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} else {
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g_blk_bound = -1;
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g_blk_capacity = 0;
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log_warn("[VBLK] no UTSM block device, blk backend degraded");
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}
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virtio_mmio_register(&g_blk_backend);
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}
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