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分类: C/C++

2014-08-04 10:40:12

首先了解一下Linux的文件操作,接下来看一下qemu对于ide设备虚拟化过程

一)学习Linux的文件操作涉及分层


-----------
虚拟文件层vfs
-----------
磁盘设备缓存(directio不存在)
----------
块设备层(包括映射,调度)
---------
块设备驱动
---------
硬件设备
----------

二)采用ide虚拟化设备后,Linux客户机文件操作涉及分层

1.客户机
-----------
虚拟文件层vfs
-----------
磁盘设备缓存(directio不存在)
----------
块设备层(包括映射,调度)
---------
块设备驱动
----------

2.Qemu
----------
硬件设备模拟
----------
映像文件格式解析
------------

3.宿主机
-----------
虚拟文件层vfs
-----------
磁盘设备缓存(directio不存在)
----------
块设备层(包括映射,调度)
---------
块设备驱动
----------
硬件设备
----------
三)采用半虚拟化virtio-blk设备后,Linux客户机文件操作涉及分层

1.客户机
-----------
虚拟文件层vfs
-----------
磁盘设备缓存(directio不存在)
-----------
虚拟化设备模型前端
----------

2.Qemu
----------
虚拟化设备模型后端
----------
映像文件格式解析
------------

3.宿主机
-----------
虚拟文件层vfs
-----------
磁盘设备缓存(directio不存在)
----------
块设备层(包括映射,调度)
---------
块设备驱动
----------
硬件设备
----------


分析qemui/o虚拟化

1.ide驱动模拟操作流程

读取相应扇区到客户机地址空间
读取0x1f0-0x1f7保存需要读取的扇区
写入0xc100-0xc10f发起DMA操作

2.qemu设备模型截获操作
虚拟机退出时,分析vm退出原因
int kvm_run(CPUState *env)
{
   case KVM_EXIT_IO:
            r = kvm_handle_io(run->io.port,
                                (uint8_t *)run + run->io.data_offset,
                                run->io.direction,
                                run->io.size,
                                run->io.count);
}

处理i/o读操作
static int kvm_handle_io(uint16_t port, void *data, int direction, int size,
                         uint32_t count)
{
      case 2:
                stw_p(ptr, cpu_inw(port));
                break;

}

uint16_t cpu_inw(pio_addr_t addr)
{
    uint16_t val;
    val = ioport_read(1, addr);
    trace_cpu_in(addr, val);
    LOG_IOPORT("inw : %04"FMT_pioaddr" %04"PRIx16"\n", addr, val);
    return val;
}

static uint32_t ioport_read(int index, uint32_t address)
{   
    static IOPortReadFunc * const default_func[3] = {
        default_ioport_readb,
        default_ioport_readw,
        default_ioport_readl
    };
    IOPortReadFunc *func = ioport_read_table[index][address];
    if (!func)
        func = default_func[index];
    return func(ioport_opaque[address], address);
}

static void cmd_read(IDEState *s, uint8_t* buf)
{
    int nb_sectors, lba;

    if (buf[0] == GPCMD_READ_10) {
        nb_sectors = ube16_to_cpu(buf + 7);
    } else {
        nb_sectors = ube32_to_cpu(buf + 6);
    }

    lba = ube32_to_cpu(buf + 2);
    if (nb_sectors == 0) {
        ide_atapi_cmd_ok(s);
        return;
    }

    ide_atapi_cmd_read(s, lba, nb_sectors, 2048);
}

static void ide_atapi_cmd_read(IDEState *s, int lba, int nb_sectors,
                               int sector_size)
{
#ifdef DEBUG_IDE_ATAPI
    printf("read %s: LBA=%d nb_sectors=%d\n", s->atapi_dma ? "dma" : "pio",
        lba, nb_sectors);
#endif
    if (s->atapi_dma) {
        ide_atapi_cmd_read_dma(s, lba, nb_sectors, sector_size);
    } else {
        ide_atapi_cmd_read_pio(s, lba, nb_sectors, sector_size);
    }
}
static void ide_atapi_cmd_read_dma(IDEState *s, int lba, int nb_sectors,
                                   int sector_size)
{
    s->lba = lba;
    s->packet_transfer_size = nb_sectors * sector_size;
    s->io_buffer_index = 0;
    s->io_buffer_size = 0;
    s->cd_sector_size = sector_size;

    bdrv_acct_start(s->bs, &s->acct, s->packet_transfer_size, BDRV_ACCT_READ);

    /* XXX: check if BUSY_STAT should be set */
    s->status = READY_STAT | SEEK_STAT | DRQ_STAT | BUSY_STAT;
    ide_dma_start(s, ide_atapi_cmd_read_dma_cb);
}
/* ATAPI DMA support */

/* XXX: handle read errors */
static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret)
{
    bm->iov.iov_base = (void *)(s->io_buffer + data_offset);
    bm->iov.iov_len = n * 4 * 512;
    qemu_iovec_init_external(&bm->qiov, &bm->iov, 1);
    bm->aiocb = bdrv_aio_readv(s->bs, (int64_t)s->lba << 2, &bm->qiov,
                               n * 4, ide_atapi_cmd_read_dma_cb, bm);
    if (!bm->aiocb) {
        /* Note: media not present is the most likely case */
        ide_atapi_cmd_error(s, SENSE_NOT_READY,
                            ASC_MEDIUM_NOT_PRESENT);
        goto eot;
    }

    return;
}
设备额模型使用异步i/o操作模拟
/**************************************************************/
/* async I/Os */

BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num,
                                 QEMUIOVector *qiov, int nb_sectors,
                                 BlockDriverCompletionFunc *cb, void *opaque)
{
    BlockDriver *drv = bs->drv;

    trace_bdrv_aio_readv(bs, sector_num, nb_sectors, opaque);

    if (!drv)
        return NULL;
    if (bdrv_check_request(bs, sector_num, nb_sectors))
        return NULL;

    return drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors, cb, opaque);
}
启动映像文件格式的读操作
static BlockDriver bdrv_qcow2 = {
    .format_name        = "qcow2",
    .instance_size      = sizeof(BDRVQcowState),
    .bdrv_probe         = qcow2_probe,
    .bdrv_open          = qcow2_open,
    .bdrv_close         = qcow2_close,
    .bdrv_create        = qcow2_create,
    .bdrv_flush         = qcow2_flush,
    .bdrv_is_allocated  = qcow2_is_allocated,
    .bdrv_set_key       = qcow2_set_key,
    .bdrv_make_empty    = qcow2_make_empty,

    .bdrv_aio_readv     = qcow2_aio_readv,
    .bdrv_aio_writev    = qcow2_aio_writev,
    .bdrv_aio_flush     = qcow2_aio_flush,
}

static BlockDriverAIOCB *qcow2_aio_readv(BlockDriverState *bs,
                                         int64_t sector_num,
                                         QEMUIOVector *qiov, int nb_sectors,
                                         BlockDriverCompletionFunc *cb,
                                         void *opaque)
{
    QCowAIOCB *acb;

    acb = qcow2_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);
    if (!acb)
        return NULL;

    qcow2_aio_read_cb(acb, 0);
    return &acb->common;
}
3.qemu设备模型截获操作注册
1)注册要截获的端口
/* size is the word size in byte */
int register_ioport_read(pio_addr_t start, int length, int size,
                         IOPortReadFunc *func, void *opaque)
{
    int i, bsize;

    if (ioport_bsize(size, &bsize)) {
        hw_error("register_ioport_read: invalid size");
        return -1;
    }
    for(i = start; i < start + length; i += size) {
        ioport_read_table[bsize][i] = func;
        if (ioport_opaque[i] != NULL && ioport_opaque[i] != opaque)
            hw_error("register_ioport_read: invalid opaque");
        ioport_opaque[i] = opaque;
    }
    return 0;
}
void ide_init_ioport(IDEBus *bus, int iobase, int iobase2)
{
    register_ioport_write(iobase, 8, 1, ide_ioport_write, bus);
    register_ioport_read(iobase, 8, 1, ide_ioport_read, bus);
    if (iobase2) {
        register_ioport_read(iobase2, 1, 1, ide_status_read, bus);
        register_ioport_write(iobase2, 1, 1, ide_cmd_write, bus);
    }

    /* data ports */
    register_ioport_write(iobase, 2, 2, ide_data_writew, bus);
    register_ioport_read(iobase, 2, 2, ide_data_readw, bus);
    register_ioport_write(iobase, 4, 4, ide_data_writel, bus);
    register_ioport_read(iobase, 4, 4, ide_data_readl, bus);
}
static EndTransferFunc* transfer_end_table[] = {
        ide_sector_read,
        ide_sector_write,
        ide_transfer_stop,
        ide_atapi_cmd_reply_end,
        ide_atapi_cmd,
        ide_dummy_transfer_stop,
};
uint32_t ide_data_readw(void *opaque, uint32_t addr)
{
    IDEBus *bus = opaque;
    IDEState *s = idebus_active_if(bus);
    uint8_t *p;
    int ret;

    /* PIO data access allowed only when DRQ bit is set */
    if (!(s->status & DRQ_STAT))
        return 0;

    p = s->data_ptr;
    ret = cpu_to_le16(*(uint16_t *)p);
    p += 2;
    s->data_ptr = p;
    if (p >= s->data_end)
        s->end_transfer_func(s);
    return ret;
}

static const struct {
    void (*handler)(IDEState *s, uint8_t *buf);
    int flags;
} atapi_cmd_table[0x100] = {
    [ 0x00 ] = { cmd_test_unit_ready,               CHECK_READY },
    [ 0x03 ] = { cmd_request_sense,                 ALLOW_UA },
    [ 0x12 ] = { cmd_inquiry,                       ALLOW_UA },
    [ 0x1a ] = { cmd_mode_sense, /* (6) */          0 },
    [ 0x1b ] = { cmd_start_stop_unit,               0 }, /* [1] */
    [ 0x1e ] = { cmd_prevent_allow_medium_removal,  0 },
    [ 0x25 ] = { cmd_read_cdvd_capacity,            CHECK_READY },
    [ 0x28 ] = { cmd_read, /* (10) */               CHECK_READY },
    [ 0x2b ] = { cmd_seek,                          CHECK_READY },
    [ 0x43 ] = { cmd_read_toc_pma_atip,             CHECK_READY },
    [ 0x46 ] = { cmd_get_configuration,             ALLOW_UA },
    [ 0x4a ] = { cmd_get_event_status_notification, ALLOW_UA },
    [ 0x5a ] = { cmd_mode_sense, /* (10) */         0 },
    [ 0xa8 ] = { cmd_read, /* (12) */               CHECK_READY },
    [ 0xad ] = { cmd_read_dvd_structure,            CHECK_READY },
    [ 0xbb ] = { cmd_set_speed,                     0 },
    [ 0xbd ] = { cmd_mechanism_status,              0 },
    [ 0xbe ] = { cmd_read_cd,                       CHECK_READY },
    /* [1] handler detects and reports not ready condition itself */
};

void ide_atapi_cmd(IDEState *s)
{
   /* Execute the command */
    if (atapi_cmd_table[s->io_buffer[0]].handler) {
        atapi_cmd_table[s->io_buffer[0]].handler(s, buf);
        return;
    }

}

http://blog.csdn.net/zhuriyuxiao/article/details/8819002
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