int bdrv_pread(BlockDriverState *bs, int64_t offset,

               void *buf1, int count1)

{

    BlockDriver *drv = bs->drv;



    if (!drv)

        return -ENOMEDIUM;

    if (!drv->bdrv_pread)

        return bdrv_pread_em(bs, offset, buf1, count1);



    return drv->bdrv_pread(bs, offset, buf1, count1);

}