Re: [Qemu-block] [Qemu-devel] [PATCH V4 1/6] ide/atapi: make PIO read requests async

[John Snow]

On 11/13/2015 06:00 PM, Peter Lieven wrote:
> 
> 
>> Am 13.11.2015 um 23:42 schrieb John Snow <address@hidden>:
>>
>>
>>
>>> On 11/12/2015 11:30 AM, Peter Lieven wrote:
>>> PIO read requests on the ATAPI interface used to be sync blk requests.
>>> This has two significant drawbacks. First the main loop hangs util an
>>> I/O request is completed and secondly if the I/O request does not
>>> complete (e.g. due to an unresponsive storage) Qemu hangs completely.
>>>
>>> Note: Due to possible race conditions requests during an ongoing
>>> elementary transfer are still sync.
>>>
>>> Signed-off-by: Peter Lieven <address@hidden>
>>> ---
>>> hw/ide/atapi.c | 97 
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++--------
>>> 1 file changed, 85 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
>>> index 747f466..cfd2d63 100644
>>> --- a/hw/ide/atapi.c
>>> +++ b/hw/ide/atapi.c
>>> @@ -105,33 +105,98 @@ static void cd_data_to_raw(uint8_t *buf, int lba)
>>>     memset(buf, 0, 288);
>>> }
>>>
>>> -static int cd_read_sector(IDEState *s, int lba, uint8_t *buf, int 
>>> sector_size)
>>> +static int
>>> +cd_read_sector_sync(IDEState *s)
>>> {
>>>     int ret;
>>>
>>> -    switch(sector_size) {
>>> +#ifdef DEBUG_IDE_ATAPI
>>> +    printf("cd_read_sector_sync: lba=%d\n", s->lba);
>>> +#endif
>>> +
>>> +    switch (s->cd_sector_size) {
>>>     case 2048:
>>>         block_acct_start(blk_get_stats(s->blk), &s->acct,
>>>                          4 * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
>>> -        ret = blk_read(s->blk, (int64_t)lba << 2, buf, 4);
>>> +        ret = blk_read(s->blk, (int64_t)s->lba << 2,
>>> +                       s->io_buffer, 4);
>>>         block_acct_done(blk_get_stats(s->blk), &s->acct);
>>>         break;
>>>     case 2352:
>>>         block_acct_start(blk_get_stats(s->blk), &s->acct,
>>>                          4 * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
>>> -        ret = blk_read(s->blk, (int64_t)lba << 2, buf + 16, 4);
>>> +        ret = blk_read(s->blk, (int64_t)s->lba << 2,
>>> +                       s->io_buffer + 16, 4);
>>>         block_acct_done(blk_get_stats(s->blk), &s->acct);
>>>         if (ret < 0)
>>>             return ret;
>>> -        cd_data_to_raw(buf, lba);
>>> +        cd_data_to_raw(s->io_buffer, s->lba);
>>>         break;
>>>     default:
>>>         ret = -EIO;
>>>         break;
>>>     }
>>> +
>>> +    if (!ret) {
>>> +        s->lba++;
>>> +        s->io_buffer_index = 0;
>>> +    }
>>> +
>>>     return ret;
>>> }
>>>
>>> +static void cd_read_sector_cb(void *opaque, int ret)
>>> +{
>>> +    IDEState *s = opaque;
>>> +
>>> +    block_acct_done(blk_get_stats(s->blk), &s->acct);
>>> +
>>> +#ifdef DEBUG_IDE_ATAPI
>>> +    printf("cd_read_sector_cb: lba=%d ret=%d\n", s->lba, ret);
>>> +#endif
>>> +
>>> +    if (ret < 0) {
>>> +        ide_atapi_io_error(s, ret);
>>> +        return;
>>> +    }
>>> +
>>> +    if (s->cd_sector_size == 2352) {
>>> +        cd_data_to_raw(s->io_buffer, s->lba);
>>> +    }
>>> +
>>> +    s->lba++;
>>> +    s->io_buffer_index = 0;
>>> +    s->status &= ~BUSY_STAT;
>>> +
>>> +    ide_atapi_cmd_reply_end(s);
>>> +}
>>> +
>>> +static int cd_read_sector(IDEState *s)
>>> +{
>>> +    if (s->cd_sector_size != 2048 && s->cd_sector_size != 2352) {
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    s->iov.iov_base = (s->cd_sector_size == 2352) ?
>>> +                      s->io_buffer + 16 : s->io_buffer;
>>> +
>>> +    s->iov.iov_len = 4 * BDRV_SECTOR_SIZE;
>>> +    qemu_iovec_init_external(&s->qiov, &s->iov, 1);
>>> +
>>> +#ifdef DEBUG_IDE_ATAPI
>>> +    printf("cd_read_sector: lba=%d\n", s->lba);
>>> +#endif
>>> +
>>> +    block_acct_start(blk_get_stats(s->blk), &s->acct,
>>> +                     4 * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
>>> +
>>> +    blk_aio_readv(s->blk, (int64_t)s->lba << 2, &s->qiov, 4,
>>> +                  cd_read_sector_cb, s);
>>> +
>>> +    s->status |= BUSY_STAT;
>>> +    return 0;
>>> +}
>>> +
>>> void ide_atapi_cmd_ok(IDEState *s)
>>> {
>>>     s->error = 0;
>>> @@ -182,18 +247,27 @@ void ide_atapi_cmd_reply_end(IDEState *s)
>>>         ide_atapi_cmd_ok(s);
>>>         ide_set_irq(s->bus);
>>> #ifdef DEBUG_IDE_ATAPI
>>> -        printf("status=0x%x\n", s->status);
>>> +        printf("end of transfer, status=0x%x\n", s->status);
>>> #endif
>>>     } else {
>>>         /* see if a new sector must be read */
>>>         if (s->lba != -1 && s->io_buffer_index >= s->cd_sector_size) {
>>> -            ret = cd_read_sector(s, s->lba, s->io_buffer, 
>>> s->cd_sector_size);
>>> -            if (ret < 0) {
>>> -                ide_atapi_io_error(s, ret);
>>> +            if (!s->elementary_transfer_size) {
>>> +                ret = cd_read_sector(s);
>>> +                if (ret < 0) {
>>> +                    ide_atapi_io_error(s, ret);
>>> +                }
>>>                 return;
>>> +            } else {
>>> +                /* rebuffering within an elementary transfer is
>>> +                 * only possible with a sync request because we
>>> +                 * end up with a race condition otherwise */
>>> +                ret = cd_read_sector_sync(s);
>>> +                if (ret < 0) {
>>> +                    ide_atapi_io_error(s, ret);
>>> +                    return;
>>> +                }
>>>             }
>>> -            s->lba++;
>>> -            s->io_buffer_index = 0;
>>>         }
>>>         if (s->elementary_transfer_size > 0) {
>>>             /* there are some data left to transmit in this elementary
>>> @@ -275,7 +349,6 @@ static void ide_atapi_cmd_read_pio(IDEState *s, int 
>>> lba, int nb_sectors,
>>>     s->io_buffer_index = sector_size;
>>>     s->cd_sector_size = sector_size;
>>>
>>> -    s->status = READY_STAT | SEEK_STAT;
>>>     ide_atapi_cmd_reply_end(s);
>>> }
>>
>> Had to rebase against Berto's patches, but nothing major. You can see my
>> rebase at:
>>
>> https://github.com/jnsnow/qemu/tree/review-plieven
>>
>> Reviewed-by: John Snow <address@hidden>
> 
> in Patch 1 the indent is off at the end. Otherwise looks good to me.
> 
> Peter 
> 

Huh, so it is. That part wasn't even in the chunk that conflicted. :\