C++ qemu_iovec_add函数代码示例

/*
 * Copies iovecs from src to the end of dst. It starts copying after skipping
 * the given number of bytes in src and copies until src is completely copied
 * or the total size of the copied iovec reaches size.The size of the last
 * copied iovec is changed in order to fit the specified total size if it isn't
 * a perfect fit already.
 */
void qemu_iovec_copy(QEMUIOVector *dst, QEMUIOVector *src, uint64_t skip,
    size_t size)
{
    int i;
    size_t done;
    void *iov_base;
    uint64_t iov_len;

    assert(dst->nalloc != -1);

    done = 0;
    for (i = 0; (i < src->niov) && (done != size); i++) {
        if (skip >= src->iov[i].iov_len) {
            /* Skip the whole iov */
            skip -= src->iov[i].iov_len;
            continue;
        } else {
            /* Skip only part (or nothing) of the iov */
            iov_base = (uint8_t*) src->iov[i].iov_base + skip;
            iov_len = src->iov[i].iov_len - skip;
            skip = 0;
        }

        if (done + iov_len > size) {
            qemu_iovec_add(dst, iov_base, size - done);
            break;
        } else {
            qemu_iovec_add(dst, iov_base, iov_len);
        }
        done += iov_len;
    }
}

/**
 * Copy contents of I/O vector
 *
 * The relative relationships of overlapping iovecs are preserved.  This is
 * necessary to ensure identical semantics in the cloned I/O vector.
 */
void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
{
    IOVectorSortElem sortelems[src->niov];
    void *last_end;
    int i;

    /* Sort by source iovecs by base address */
    for (i = 0; i < src->niov; i++) {
        sortelems[i].src_index = i;
        sortelems[i].src_iov = &src->iov[i];
    }
    qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);

    /* Allocate buffer space taking into account overlapping iovecs */
    last_end = NULL;
    for (i = 0; i < src->niov; i++) {
        struct iovec *cur = sortelems[i].src_iov;
        ptrdiff_t rewind = 0;

        /* Detect overlap */
        if (last_end && last_end > cur->iov_base) {
            rewind = last_end - cur->iov_base;
        }

        sortelems[i].dest_base = buf - rewind;
        buf += cur->iov_len - MIN(rewind, cur->iov_len);
        last_end = MAX(cur->iov_base + cur->iov_len, last_end);
    }

    /* Sort by source iovec index and build destination iovec */
    qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
    for (i = 0; i < src->niov; i++) {
        qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
    }
}

int usb_packet_map(USBPacket *p, QEMUSGList *sgl)
{
    DMADirection dir = (p->pid == USB_TOKEN_IN) ?
        DMA_DIRECTION_FROM_DEVICE : DMA_DIRECTION_TO_DEVICE;
    dma_addr_t len;
    void *mem;
    int i;

    for (i = 0; i < sgl->nsg; i++) {
        len = sgl->sg[i].len;
        mem = dma_memory_map(sgl->dma, sgl->sg[i].base, &len, dir);
        if (!mem) {
            goto err;
        }
        qemu_iovec_add(&p->iov, mem, len);
        if (len != sgl->sg[i].len) {
            goto err;
        }
    }
    return 0;

err:
    usb_packet_unmap(p, sgl);
    return -1;
}

static int coroutine_fn
raw_co_writev_flags(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
                    QEMUIOVector *qiov, int flags)
{
    void *buf = NULL;
    BlockDriver *drv;
    QEMUIOVector local_qiov;
    int ret;

    if (bs->probed && sector_num == 0) {
        /* As long as these conditions are true, we can't get partial writes to
         * the probe buffer and can just directly check the request. */
        QEMU_BUILD_BUG_ON(BLOCK_PROBE_BUF_SIZE != 512);
        QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != 512);

        if (nb_sectors == 0) {
            /* qemu_iovec_to_buf() would fail, but we want to return success
             * instead of -EINVAL in this case. */
            return 0;
        }

        buf = qemu_try_blockalign(bs->file->bs, 512);
        if (!buf) {
            ret = -ENOMEM;
            goto fail;
        }

        ret = qemu_iovec_to_buf(qiov, 0, buf, 512);
        if (ret != 512) {
            ret = -EINVAL;
            goto fail;
        }

        drv = bdrv_probe_all(buf, 512, NULL);
        if (drv != bs->drv) {
            ret = -EPERM;
            goto fail;
        }

        /* Use the checked buffer, a malicious guest might be overwriting its
         * original buffer in the background. */
        qemu_iovec_init(&local_qiov, qiov->niov + 1);
        qemu_iovec_add(&local_qiov, buf, 512);
        qemu_iovec_concat(&local_qiov, qiov, 512, qiov->size - 512);
        qiov = &local_qiov;
    }

    BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
    ret = bdrv_co_do_pwritev(bs->file->bs, sector_num * BDRV_SECTOR_SIZE,
                             nb_sectors * BDRV_SECTOR_SIZE, qiov, flags);

fail:
    if (qiov == &local_qiov) {
        qemu_iovec_destroy(&local_qiov);
    }
    qemu_vfree(buf);
    return ret;
}

/*
 * Copies iovecs from src to the end dst until src is completely copied or the
 * total size of the copied iovec reaches size. The size of the last copied
 * iovec is changed in order to fit the specified total size if it isn't a
 * perfect fit already.
 */
void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size)
{
    int i;
    size_t done;

    assert(dst->nalloc != -1);

    done = 0;
    for (i = 0; (i < src->niov) && (done != size); i++) {
        if (done + src->iov[i].iov_len > size) {
            qemu_iovec_add(dst, src->iov[i].iov_base, size - done);
            break;
        } else {
            qemu_iovec_add(dst, src->iov[i].iov_base, src->iov[i].iov_len);
        }
        done += src->iov[i].iov_len;
    }
}

static void dma_bdrv_cb(void *opaque, int ret)
{
    DMAAIOCB *dbs = (DMAAIOCB *)opaque;
    target_phys_addr_t cur_addr, cur_len;
    void *mem;

    dbs->acb = NULL;
    dbs->sector_num += dbs->iov.size / 512;
    dma_bdrv_unmap(dbs);
    qemu_iovec_reset(&dbs->iov);

    if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
        dbs->common.cb(dbs->common.opaque, ret);
        qemu_iovec_destroy(&dbs->iov);
        qemu_aio_release(dbs);
        return;
    }

    while (dbs->sg_cur_index < dbs->sg->nsg) {
        cur_addr = dbs->sg->sg[dbs->sg_cur_index].base + dbs->sg_cur_byte;
        cur_len = dbs->sg->sg[dbs->sg_cur_index].len - dbs->sg_cur_byte;
        mem = cpu_physical_memory_map(cur_addr, &cur_len, !dbs->is_write);
        if (!mem)
            break;
        qemu_iovec_add(&dbs->iov, mem, cur_len);
        dbs->sg_cur_byte += cur_len;
        if (dbs->sg_cur_byte == dbs->sg->sg[dbs->sg_cur_index].len) {
            dbs->sg_cur_byte = 0;
            ++dbs->sg_cur_index;
        }
    }

    if (dbs->iov.size == 0) {
        cpu_register_map_client(dbs, continue_after_map_failure);
        return;
    }

    if (dbs->is_write) {
        dbs->acb = bdrv_aio_writev(dbs->bs, dbs->sector_num, &dbs->iov,
                                   dbs->iov.size / 512, dma_bdrv_cb, dbs);
    } else {
        dbs->acb = bdrv_aio_readv(dbs->bs, dbs->sector_num, &dbs->iov,
                                  dbs->iov.size / 512, dma_bdrv_cb, dbs);
    }
    if (!dbs->acb) {
        dma_bdrv_unmap(dbs);
        qemu_iovec_destroy(&dbs->iov);
        return;
    }
}

static inline void flash_sync_area(Flash *s, int64_t off, int64_t len)
{
    QEMUIOVector *iov;

    if (!s->blk || blk_is_read_only(s->blk)) {
        return;
    }

    assert(!(len % BDRV_SECTOR_SIZE));
    iov = g_new(QEMUIOVector, 1);
    qemu_iovec_init(iov, 1);
    qemu_iovec_add(iov, s->storage + off, len);
    blk_aio_pwritev(s->blk, off, iov, 0, blk_sync_complete, iov);
}

static void flash_sync_page(Flash *s, int page)
{
    QEMUIOVector *iov;

    if (!s->blk || blk_is_read_only(s->blk)) {
        return;
    }

    iov = g_new(QEMUIOVector, 1);
    qemu_iovec_init(iov, 1);
    qemu_iovec_add(iov, s->storage + page * s->pi->page_size,
                   s->pi->page_size);
    blk_aio_pwritev(s->blk, page * s->pi->page_size, iov, 0,
                    blk_sync_complete, iov);
}

/*
 * Parse multiple length statements for vectored I/O, and construct an I/O
 * vector matching it.
 */
static void *
create_iovec(QEMUIOVector *qiov, char **argv, int nr_iov, int pattern)
{
    size_t *sizes = g_new0(size_t, nr_iov);
    size_t count = 0;
    void *buf = NULL;
    void *p;
    int i;

    for (i = 0; i < nr_iov; i++) {
        char *arg = argv[i];
        int64_t len;

        len = cvtnum(arg);
        if (len < 0) {
            printf("non-numeric length argument -- %s\n", arg);
            goto fail;
        }

        /* should be SIZE_T_MAX, but that doesn't exist */
        if (len > INT_MAX) {
            printf("too large length argument -- %s\n", arg);
            goto fail;
        }

        if (len & 0x1ff) {
            printf("length argument %" PRId64
                   " is not sector aligned\n", len);
            goto fail;
        }

        sizes[i] = len;
        count += len;
    }

    qemu_iovec_init(qiov, nr_iov);

    buf = p = qemu_io_alloc(count, pattern);

    for (i = 0; i < nr_iov; i++) {
        qemu_iovec_add(qiov, p, sizes[i]);
        p += sizes[i];
    }

fail:
    g_free(sizes);
    return buf;
}

static void dma_blk_cb(void *opaque, int ret)
{
    DMAAIOCB *dbs = (DMAAIOCB *)opaque;
    dma_addr_t cur_addr, cur_len;
    void *mem;

    trace_dma_blk_cb(dbs, ret);

    dbs->acb = NULL;
    dbs->sector_num += dbs->iov.size / 512;

    if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
        dma_complete(dbs, ret);
        return;
    }
    dma_blk_unmap(dbs);

    while (dbs->sg_cur_index < dbs->sg->nsg) {
        cur_addr = dbs->sg->sg[dbs->sg_cur_index].base + dbs->sg_cur_byte;
        cur_len = dbs->sg->sg[dbs->sg_cur_index].len - dbs->sg_cur_byte;
        mem = dma_memory_map(dbs->sg->as, cur_addr, &cur_len, dbs->dir);
        if (!mem)
            break;
        qemu_iovec_add(&dbs->iov, mem, cur_len);
        dbs->sg_cur_byte += cur_len;
        if (dbs->sg_cur_byte == dbs->sg->sg[dbs->sg_cur_index].len) {
            dbs->sg_cur_byte = 0;
            ++dbs->sg_cur_index;
        }
    }

    if (dbs->iov.size == 0) {
        trace_dma_map_wait(dbs);
        dbs->bh = aio_bh_new(blk_get_aio_context(dbs->blk),
                             reschedule_dma, dbs);
        cpu_register_map_client(dbs->bh);
        return;
    }

    if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
        qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & ~BDRV_SECTOR_MASK);
    }

    dbs->acb = dbs->io_func(dbs->blk, dbs->sector_num, &dbs->iov,
                            dbs->iov.size / 512, dma_blk_cb, dbs);
    assert(dbs->acb);
}

static void flash_sync_page(Flash *s, int page)
{
    int blk_sector, nb_sectors;
    QEMUIOVector iov;

    if (!s->blk || blk_is_read_only(s->blk)) {
        return;
    }

    blk_sector = (page * s->pi->page_size) / BDRV_SECTOR_SIZE;
    nb_sectors = DIV_ROUND_UP(s->pi->page_size, BDRV_SECTOR_SIZE);
    qemu_iovec_init(&iov, 1);
    qemu_iovec_add(&iov, s->storage + blk_sector * BDRV_SECTOR_SIZE,
                   nb_sectors * BDRV_SECTOR_SIZE);
    blk_aio_writev(s->blk, blk_sector, &iov, nb_sectors, blk_sync_complete,
                   NULL);
}

static inline void submit_requests(BlockBackend *blk, MultiReqBuffer *mrb,
                                   int start, int num_reqs, int niov)
{
    QEMUIOVector *qiov = &mrb->reqs[start]->qiov;
    int64_t sector_num = mrb->reqs[start]->sector_num;
    int nb_sectors = mrb->reqs[start]->qiov.size / BDRV_SECTOR_SIZE;
    bool is_write = mrb->is_write;

    if (num_reqs > 1) {
        int i;
        struct iovec *tmp_iov = qiov->iov;
        int tmp_niov = qiov->niov;

        /* mrb->reqs[start]->qiov was initialized from external so we can't
         * modifiy it here. We need to initialize it locally and then add the
         * external iovecs. */
        qemu_iovec_init(qiov, niov);

        for (i = 0; i < tmp_niov; i++) {
            qemu_iovec_add(qiov, tmp_iov[i].iov_base, tmp_iov[i].iov_len);
        }

        for (i = start + 1; i < start + num_reqs; i++) {
            qemu_iovec_concat(qiov, &mrb->reqs[i]->qiov, 0,
                              mrb->reqs[i]->qiov.size);
            mrb->reqs[i - 1]->mr_next = mrb->reqs[i];
            nb_sectors += mrb->reqs[i]->qiov.size / BDRV_SECTOR_SIZE;
        }
        assert(nb_sectors == qiov->size / BDRV_SECTOR_SIZE);

        trace_virtio_blk_submit_multireq(mrb, start, num_reqs, sector_num,
                                         nb_sectors, is_write);
        block_acct_merge_done(blk_get_stats(blk),
                              is_write ? BLOCK_ACCT_WRITE : BLOCK_ACCT_READ,
                              num_reqs - 1);
    }

    if (is_write) {
        blk_aio_writev(blk, sector_num, qiov, nb_sectors,
                       virtio_blk_rw_complete, mrb->reqs[start]);
    } else {
        blk_aio_readv(blk, sector_num, qiov, nb_sectors,
                      virtio_blk_rw_complete, mrb->reqs[start]);
    }
}

static inline void flash_sync_area(Flash *s, int64_t off, int64_t len)
{
    int64_t start, end, nb_sectors;
    QEMUIOVector iov;

    if (!s->blk || blk_is_read_only(s->blk)) {
        return;
    }

    assert(!(len % BDRV_SECTOR_SIZE));
    start = off / BDRV_SECTOR_SIZE;
    end = (off + len) / BDRV_SECTOR_SIZE;
    nb_sectors = end - start;
    qemu_iovec_init(&iov, 1);
    qemu_iovec_add(&iov, s->storage + (start * BDRV_SECTOR_SIZE),
                                        nb_sectors * BDRV_SECTOR_SIZE);
    blk_aio_writev(s->blk, start, &iov, nb_sectors, blk_sync_complete, NULL);
}

/*
 * Concatenates (partial) iovecs from src to the end of dst.
 * It starts copying after skipping `soffset' bytes at the
 * beginning of src and adds individual vectors from src to
 * dst copies up to `sbytes' bytes total, or up to the end
 * of src if it comes first.  This way, it is okay to specify
 * very large value for `sbytes' to indicate "up to the end
 * of src".
 * Only vector pointers are processed, not the actual data buffers.
 */
void qemu_iovec_concat(QEMUIOVector *dst,
                       QEMUIOVector *src, size_t soffset, size_t sbytes)
{
    int i;
    size_t done;
    struct iovec *siov = src->iov;
    assert(dst->nalloc != -1);
    assert(src->size >= soffset);
    for (i = 0, done = 0; done < sbytes && i < src->niov; i++) {
        if (soffset < siov[i].iov_len) {
            size_t len = MIN(siov[i].iov_len - soffset, sbytes - done);
            qemu_iovec_add(dst, siov[i].iov_base + soffset, len);
            done += len;
            soffset = 0;
        } else {
            soffset -= siov[i].iov_len;
        }
    }
    /* return done; */
}

static void dma_bdrv_cb(void *opaque, int ret)
{
    DMAAIOCB *dbs = (DMAAIOCB *)opaque;
    dma_addr_t cur_addr, cur_len;
    void *mem;

    trace_dma_bdrv_cb(dbs, ret);

    dbs->acb = NULL;
    dbs->sector_num += dbs->iov.size / 512;
    dma_bdrv_unmap(dbs);

    if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
        dma_complete(dbs, ret);
        return;
    }

    while (dbs->sg_cur_index < dbs->sg->nsg) {
        cur_addr = dbs->sg->sg[dbs->sg_cur_index].base + dbs->sg_cur_byte;
        cur_len = dbs->sg->sg[dbs->sg_cur_index].len - dbs->sg_cur_byte;
        mem = dma_memory_map(dbs->sg->dma, cur_addr, &cur_len, dbs->dir);
        if (!mem)
            break;
        qemu_iovec_add(&dbs->iov, mem, cur_len);
        dbs->sg_cur_byte += cur_len;
        if (dbs->sg_cur_byte == dbs->sg->sg[dbs->sg_cur_index].len) {
            dbs->sg_cur_byte = 0;
            ++dbs->sg_cur_index;
        }
    }

    if (dbs->iov.size == 0) {
        trace_dma_map_wait(dbs);
        cpu_register_map_client(dbs, continue_after_map_failure);
        return;
    }

    dbs->acb = dbs->io_func(dbs->bs, dbs->sector_num, &dbs->iov,
                            dbs->iov.size / 512, dma_bdrv_cb, dbs);
    assert(dbs->acb);
}