Re: [Qemu-devel] [PATCH 3/3] ide: really restart pending and in-flight atapi dma

[John Snow]

On 03/23/2016 06:26 AM, Denis V. Lunev wrote:
> From: Pavel Butsykin <address@hidden>
> 
> Restart of ATAPI DMA used to be unreachable, because the request to do
> so wasn't indicated in bus->error_status due to the lack of spare bits, and
> ide_restart_bh() would return early doing nothing.
> 
> This patch makes use of the observation that not all bit combinations were
> possible in ->error_status. In particular, IDE_RETRY_READ only made sense
> together with IDE_RETRY_DMA or IDE_RETRY_PIO. This allows to re-use
> IDE_RETRY_READ alone as an indicator of ATAPI DMA restart request.
> 
> As a means against confusion, macros are added to test the state of
> ->error_status.
> 
> The patch fixes the restart of both in-flight and pending ATAPI DMA,
> following the scheme similar to that of IDE DMA.
> 
> Signed-off-by: Pavel Butsykin <address@hidden>
> Reviewed-by: Roman Kagan <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: John Snow <address@hidden>
> ---
>  hw/ide/atapi.c    | 15 +++++++--------
>  hw/ide/core.c     | 23 ++++++++++-------------
>  hw/ide/internal.h | 18 ++++++++++++++++++
>  3 files changed, 35 insertions(+), 21 deletions(-)
> 
> diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
> index 8816b38..0d51b44 100644
> --- a/hw/ide/atapi.c
> +++ b/hw/ide/atapi.c
> @@ -375,22 +375,25 @@ static void ide_atapi_cmd_check_status(IDEState *s)
>  }
>  /* ATAPI DMA support */
>  
> -/* XXX: handle read errors */
>  static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret)
>  {
>      IDEState *s = opaque;
>      int data_offset, n;
>  
> -    if (ret < 0) { /* XXX: handle -ESTATESAVE for migration */
> +    if (ret < 0) {
>          if (ret == -ESTATESAVE) {
>              /*
>               * This case is not really an error
>               * but a request to save the state.
>               */
> +            s->bus->error_status = IDE_RETRY_ATAPI;
>              return;
> +        } else if (ide_handle_rw_error(s, -ret, IDE_RETRY_ATAPI)) {
> +            if (s->bus->error_status) {
> +                return;
> +            }
> +            goto eot;
>          }
> -        ide_atapi_io_error(s, ret);
> -        goto eot;
>      }
>  
>      if (s->io_buffer_size > 0) {
> @@ -488,10 +491,6 @@ static void ide_atapi_cmd_read(IDEState *s, int lba, int 
> nb_sectors,
>      }
>  }
>  
> -
> -/* Called by *_restart_bh when the transfer function points
> - * to ide_atapi_cmd
> - */
>  void ide_atapi_dma_restart(IDEState *s)
>  {
>      /*
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 872e11f..6d7533f 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -56,7 +56,6 @@ static const int smart_attributes[][12] = {
>      { 190,  0x03, 0x00, 0x45, 0x45, 0x1f, 0x00, 0x1f, 0x1f, 0x00, 0x00, 
> 0x32},
>  };
>  
> -static int ide_handle_rw_error(IDEState *s, int error, int op);
>  static void ide_dummy_transfer_stop(IDEState *s);
>  
>  static void padstr(char *str, const char *src, int len)
> @@ -772,7 +771,7 @@ void ide_dma_error(IDEState *s)
>      ide_set_irq(s->bus);
>  }
>  
> -static int ide_handle_rw_error(IDEState *s, int error, int op)
> +int ide_handle_rw_error(IDEState *s, int error, int op)
>  {
>      bool is_read = (op & IDE_RETRY_READ) != 0;
>      BlockErrorAction action = blk_get_error_action(s->blk, is_read, error);
> @@ -782,8 +781,10 @@ static int ide_handle_rw_error(IDEState *s, int error, 
> int op)
>          s->bus->error_status = op;
>      } else if (action == BLOCK_ERROR_ACTION_REPORT) {
>          block_acct_failed(blk_get_stats(s->blk), &s->acct);
> -        if (op & IDE_RETRY_DMA) {
> +        if (IS_IDE_RETRY_DMA(op)) {
>              ide_dma_error(s);
> +        } else if (IS_IDE_RETRY_ATAPI(op)) {
> +            ide_atapi_io_error(s, -error);
>          } else {
>              ide_rw_error(s);
>          }
> @@ -2533,13 +2534,13 @@ static void ide_restart_bh(void *opaque)
>          }
>      }
>  
> -    if (error_status & IDE_RETRY_DMA) {
> +    if (IS_IDE_RETRY_DMA(error_status)) {
>          if (error_status & IDE_RETRY_TRIM) {
>              ide_restart_dma(s, IDE_DMA_TRIM);
>          } else {
>              ide_restart_dma(s, is_read ? IDE_DMA_READ : IDE_DMA_WRITE);
>          }
> -    } else if (error_status & IDE_RETRY_PIO) {
> +    } else if (IS_IDE_RETRY_PIO(error_status)) {
>          if (is_read) {
>              ide_sector_read(s);
>          } else {
> @@ -2547,15 +2548,11 @@ static void ide_restart_bh(void *opaque)
>          }
>      } else if (error_status & IDE_RETRY_FLUSH) {
>          ide_flush_cache(s);
> +    } else if (IS_IDE_RETRY_ATAPI(error_status)) {
> +        assert(s->end_transfer_func == ide_atapi_cmd);
> +        ide_atapi_dma_restart(s);
>      } else {
> -        /*
> -         * We've not got any bits to tell us about ATAPI - but
> -         * we do have the end_transfer_func that tells us what
> -         * we're trying to do.
> -         */
> -        if (s->end_transfer_func == ide_atapi_cmd) {
> -            ide_atapi_dma_restart(s);
> -        }
> +        abort();
>      }
>  }
>  
> diff --git a/hw/ide/internal.h b/hw/ide/internal.h
> index dcd8627..2e845d0 100644
> --- a/hw/ide/internal.h
> +++ b/hw/ide/internal.h
> @@ -508,11 +508,27 @@ struct IDEDevice {
>  /* These are used for the error_status field of IDEBus */
>  #define IDE_RETRY_DMA  0x08
>  #define IDE_RETRY_PIO  0x10
> +#define IDE_RETRY_ATAPI 0x20 /* reused IDE_RETRY_READ bit */
>  #define IDE_RETRY_READ  0x20
>  #define IDE_RETRY_FLUSH 0x40
>  #define IDE_RETRY_TRIM 0x80
>  #define IDE_RETRY_HBA  0x100
>  
> +#define IS_IDE_RETRY_DMA(_status) \
> +    ((_status) & IDE_RETRY_DMA)
> +
> +#define IS_IDE_RETRY_PIO(_status) \
> +    ((_status) & IDE_RETRY_PIO)
> +
> +/*
> + * The method of the IDE_RETRY_ATAPI determination is to use a previously
> + * impossible bit combination as a new status value.
> + */
> +#define IS_IDE_RETRY_ATAPI(_status)   \
> +    (((_status) & IDE_RETRY_ATAPI) && \
> +     !IS_IDE_RETRY_DMA(_status) &&    \
> +     !IS_IDE_RETRY_PIO(_status))
> +
>  /*
>   * a code to trigger entering error path and save/restore the "ready to DMA"
>   * state just like DMA-ing state. (Ab)use EINPROGRESS as it's not supposed to
> @@ -604,4 +620,6 @@ void ide_bus_new(IDEBus *idebus, size_t idebus_size, 
> DeviceState *dev,
>                   int bus_id, int max_units);
>  IDEDevice *ide_create_drive(IDEBus *bus, int unit, DriveInfo *drive);
>  
> +int ide_handle_rw_error(IDEState *s, int error, int op);
> +
>  #endif /* HW_IDE_INTERNAL_H */
> 

Sorry, this causes "make check" to fail on the AHCI test.

Try this:

export QTEST_QEMU_BINARY ./x86_64-softmmu/qemu-system-x86_64
make tests/ahci-test
./tests/ahci-test -p /x86_64/ahci/io/ncq/retry

The QEMU instance aborts in hw/ide/core.c line 2555,
function 'ide_restart_bh'

    } else {
        abort(); <-- here.
    }