On 09/21/2015 08:25 AM, Peter Lieven wrote:
> PIO read requests on the ATAPI interface used to be sync blk requests.
> This has to siginificant 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.
>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> hw/ide/atapi.c | 69
> ++++++++++++++++++++++++++++++++++++----------------------
> 1 file changed, 43 insertions(+), 26 deletions(-)
>
> diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
> index 747f466..9257e1c 100644
> --- a/hw/ide/atapi.c
> +++ b/hw/ide/atapi.c
> @@ -105,31 +105,51 @@ 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 void cd_read_sector_cb(void *opaque, int ret)
> {
> - int ret;
> + IDEState *s = opaque;
>
> - switch(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);
> - 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);
> - block_acct_done(blk_get_stats(s->blk), &s->acct);
> - if (ret < 0)
> - return ret;
> - cd_data_to_raw(buf, lba);
> - break;
> - default:
> - ret = -EIO;
> - break;
> + block_acct_done(blk_get_stats(s->blk), &s->acct);
> +
> + 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);
> }
> - return ret;
> +
> + s->lba++;
> + s->io_buffer_index = 0;
> + s->status &= ~BUSY_STAT;
> +
> + ide_atapi_cmd_reply_end(s);
> +}
> +
> +static int cd_read_sector(IDEState *s, int lba, void *buf, int sector_size)
> +{
> + if (sector_size != 2048 && sector_size != 2352) {
> + return -EINVAL;
> + }
> +
> + s->iov.iov_base = buf;
> + if (sector_size == 2352) {
> + buf += 4;
> + }
> +
> + s->iov.iov_len = 4 * BDRV_SECTOR_SIZE;
> + qemu_iovec_init_external(&s->qiov, &s->iov, 1);
> +
> + if (blk_aio_readv(s->blk, (int64_t)lba << 2, &s->qiov, 4,
> + cd_read_sector_cb, s) == NULL) {
> + return -EIO;
> + }
> +
> + block_acct_start(blk_get_stats(s->blk), &s->acct,
> + 4 * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
> + s->status |= BUSY_STAT;
> + return 0;
> }
>
We discussed this off-list a bit, but for upstream synchronization:
Unfortunately, I believe making cd_read_sector here non-blocking makes
ide_atapi_cmd_reply_end non-blocking, and as a result makes calls to
s->end_transfer_func() nonblocking, which functions like ide_data_readw
are not prepared to cope with.
My suggestion is to buffer an entire DRQ block of data at once
(byte_count_limit) to avoid the problem.
Thanks,
--js
> void ide_atapi_cmd_ok(IDEState *s)
> @@ -190,10 +210,8 @@ void ide_atapi_cmd_reply_end(IDEState *s)
> ret = cd_read_sector(s, s->lba, s->io_buffer, s->cd_sector_size);
> if (ret < 0) {
> ide_atapi_io_error(s, ret);
> - return;
> }
> - s->lba++;
> - s->io_buffer_index = 0;
> + return;
> }
> if (s->elementary_transfer_size > 0) {
> /* there are some data left to transmit in this elementary
> @@ -275,7 +293,6 @@ 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);
> }
>
>
