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@@ -252,3 +252,199 @@ void virtio_blk_backend_init(void) {
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virtio_mmio_register(&g_blk_backend);
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}
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/* ===== Memory-backed rootfs virtio-blk 后端 =====
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*
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* 第二个 virtio-blk 设备，后端为内存中的 Arch rootfs 镜像（Limine boot module）。
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* guest 看到 /dev/vdb，挂载为真实根文件系统（ext4），switch_root 进入 Arch。
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*
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* 读写直接操作内存（memcpy），无需块设备 API。 */
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/* byte-wise memcpy helper (freestanding, no libc) */
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static void rf_memcpy(void *dst, const void *src, u64 n) {
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u8 *d = (u8 *)dst;
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const u8 *s = (const u8 *)src;
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while (n--) *d++ = *s++;
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}
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static const u8 *g_rootfs_data; /* rootfs 镜像内存指针（HHDM 虚拟地址） */
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static u64 g_rootfs_size; /* rootfs 镜像大小（字节） */
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static u64 g_rootfs_capacity; /* rootfs 容量（扇区数，512B 单位） */
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static u32 rootfs_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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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_rootfs_capacity;
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cfg.size_max = 128;
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cfg.seg_max = 32;
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cfg.blk_size = 512;
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if (offset + 4 <= sizeof(cfg)) {
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u32 val = 0;
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rf_memcpy(&val, c + offset, 4);
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return val;
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}
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if (offset < sizeof(cfg)) {
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u32 val = 0;
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rf_memcpy(&val, c + offset, 4);
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return val;
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}
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return 0;
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}
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/* rootfs 请求处理：直接内存拷贝 */
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static u32 rootfs_blk_handle_chain(struct virtq_desc *desc, u16 head, u32 qnum) {
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(void)qnum;
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struct virtio_blk_outhdr hdr;
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u8 *hptr = (u8 *)virtio_gpa_to_host(desc[head].addr);
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if (!hptr) return 0;
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rf_memcpy(&hdr, hptr, sizeof(hdr));
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u32 type = hdr.type;
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u64 sector = hdr.sector;
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u16 data_idx = 0xFFFF;
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u16 status_idx = 0xFFFF;
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if (desc[head].flags & VIRTQ_DESC_F_NEXT) {
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data_idx = desc[head].next;
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u16 cur = data_idx;
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int hops = 0;
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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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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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switch (type) {
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case VIRTIO_BLK_T_IN: { /* 读：rootfs 内存 → guest */
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if (data_idx == 0xFFFF || !g_rootfs_data) {
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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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u64 offset = sector * 512ULL;
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if (offset + dlen > g_rootfs_size) {
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/* 超出范围：截断或填零 */
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u64 avail = (offset < g_rootfs_size) ? (g_rootfs_size - offset) : 0;
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if (avail > 0) {
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rf_memcpy(dbuf, g_rootfs_data + offset, avail);
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}
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/* 剩余部分填零 */
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if (dlen > avail) {
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u8 *p = dbuf + avail;
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u32 rem = dlen - (u32)avail;
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while (rem--) *p++ = 0;
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}
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bytes_done = dlen;
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} else {
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rf_memcpy(dbuf, g_rootfs_data + offset, dlen);
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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：暂不支持（rootfs 只读） */
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result = VIRTIO_BLK_S_IOERR;
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break;
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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-ROOTFS";
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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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case VIRTIO_BLK_T_FLUSH:
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result = VIRTIO_BLK_S_OK;
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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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if (status) *status = result;
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return bytes_done;
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}
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static u16 g_rootfs_last_avail;
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static void rootfs_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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u16 cur = g_rootfs_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 = rootfs_blk_handle_chain(desc, head, qnum);
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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_rootfs_last_avail = cur;
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}
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static void rootfs_blk_reset(void) {
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g_rootfs_last_avail = 0;
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}
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static struct virtio_backend g_rootfs_blk_backend = {
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.device_id = VIRTIO_ID_BLOCK,
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.gpa_base = VIRTIO_MMIO_ROOTFS_GPA,
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.irq = 7, /* guest ISA IRQ7（cmdline :7，vector 0x37） */
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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 = rootfs_blk_read_config,
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.queue_notify = rootfs_blk_queue_notify,
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.reset = rootfs_blk_reset,
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};
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void virtio_rootfs_blk_init(void) {
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u64 rootfs_size = 0;
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void *rootfs = linux_find_rootfs_module(&rootfs_size);
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if (!rootfs || rootfs_size == 0) {
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log_warn("[VBLK] no rootfs module, rootfs-blk backend not registered");
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return;
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}
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g_rootfs_data = (const u8 *)rootfs;
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g_rootfs_size = rootfs_size;
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g_rootfs_capacity = rootfs_size / 512; /* 扇区数 */
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if (rootfs_size % 512) g_rootfs_capacity++;
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log_info("[VBLK] rootfs-blk backend bound to memory module");
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log_hex64("[VBLK] rootfs size=", rootfs_size);
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log_hex64("[VBLK] rootfs capacity(sectors)=", g_rootfs_capacity);
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virtio_mmio_register(&g_rootfs_blk_backend);
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}
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