Re: [Qemu-devel] [PATCH v2 3/8] fdc: Introduce fdctrl->phase

[John Snow <jsnow@redhat.com>]

On 05/21/2015 09:19 AM, Kevin Wolf wrote:
> The floppy controller spec describes three different controller phases,
> which are currently not explicitly modelled in our emulation. Instead,
> each phase is represented by a combination of flags in registers.
> 
> This patch makes explicit in which phase the controller currently is.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/block/fdc.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 89 insertions(+)
> 
> diff --git a/hw/block/fdc.c b/hw/block/fdc.c
> index 8c41434..f5bcf0b 100644
> --- a/hw/block/fdc.c
> +++ b/hw/block/fdc.c
> @@ -495,6 +495,33 @@ enum {
>      FD_DIR_DSKCHG   = 0x80,
>  };
>  
> +/*
> + * See chapter 5.0 "Controller phases" of the spec:
> + *
> + * Command phase:
> + * The host writes a command and its parameters into the FIFO. The command
> + * phase is completed when all parameters for the command have been supplied,
> + * and execution phase is entered.
> + *
> + * Execution phase:
> + * Data transfers, either DMA or non-DMA. For non-DMA transfers, the FIFO
> + * contains the payload now, otherwise it's unused. When all bytes of the
> + * required data have been transferred, the state is switched to either result
> + * phase (if the command produces status bytes) or directly back into the
> + * command phase for the next command.
> + *
> + * Result phase:
> + * The host reads out the FIFO, which contains one or more result bytes now.
> + */
> +enum {
> +    /* Only for migration: reconstruct phase from registers like qemu 2.3 */
> +    FD_PHASE_RECONSTRUCT    = 0,
> +
> +    FD_PHASE_COMMAND        = 1,
> +    FD_PHASE_EXECUTION      = 2,
> +    FD_PHASE_RESULT         = 3,
> +};
> +
>  #define FD_MULTI_TRACK(state) ((state) & FD_STATE_MULTI)
>  #define FD_FORMAT_CMD(state) ((state) & FD_STATE_FORMAT)
>  
> @@ -504,6 +531,7 @@ struct FDCtrl {
>      /* Controller state */
>      QEMUTimer *result_timer;
>      int dma_chann;
> +    uint8_t phase;
>      /* Controller's identification */
>      uint8_t version;
>      /* HW */
> @@ -744,6 +772,28 @@ static const VMStateDescription vmstate_fdrive = {
>      }
>  };
>  
> +/*
> + * Reconstructs the phase from register values according to the logic that was
> + * implemented in qemu 2.3. This is the default value that is used if the phase
> + * subsection is not present on migration.
> + *
> + * Don't change this function to reflect newer qemu versions, it is part of
> + * the migration ABI.
> + */
> +static int reconstruct_phase(FDCtrl *fdctrl)
> +{
> +    if (fdctrl->msr & FD_MSR_NONDMA) {
> +        return FD_PHASE_EXECUTION;
> +    } else if ((fdctrl->msr & FD_MSR_RQM) == 0) {
> +        /* qemu 2.3 disabled RQM only during DMA transfers */
> +        return FD_PHASE_EXECUTION;
> +    } else if (fdctrl->msr & FD_MSR_DIO) {
> +        return FD_PHASE_RESULT;
> +    } else {
> +        return FD_PHASE_COMMAND;
> +    }
> +}
> +
>  static void fdc_pre_save(void *opaque)
>  {
>      FDCtrl *s = opaque;
> @@ -751,12 +801,24 @@ static void fdc_pre_save(void *opaque)
>      s->dor_vmstate = s->dor | GET_CUR_DRV(s);
>  }
>  
> +static int fdc_pre_load(void *opaque)
> +{
> +    FDCtrl *s = opaque;
> +    s->phase = FD_PHASE_RECONSTRUCT;
> +    return 0;
> +}
> +
>  static int fdc_post_load(void *opaque, int version_id)
>  {
>      FDCtrl *s = opaque;
>  
>      SET_CUR_DRV(s, s->dor_vmstate & FD_DOR_SELMASK);
>      s->dor = s->dor_vmstate & ~FD_DOR_SELMASK;
> +
> +    if (s->phase == FD_PHASE_RECONSTRUCT) {
> +        s->phase = reconstruct_phase(s);
> +    }
> +
>      return 0;
>  }
>  
> @@ -794,11 +856,29 @@ static const VMStateDescription vmstate_fdc_result_timer = {
>      }
>  };
>  
> +static bool fdc_phase_needed(void *opaque)
> +{
> +    FDCtrl *fdctrl = opaque;
> +
> +    return reconstruct_phase(fdctrl) != fdctrl->phase;
> +}
> +
> +static const VMStateDescription vmstate_fdc_phase = {
> +    .name = "fdc/phase",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT8(phase, FDCtrl),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static const VMStateDescription vmstate_fdc = {
>      .name = "fdc",
>      .version_id = 2,
>      .minimum_version_id = 2,
>      .pre_save = fdc_pre_save,
> +    .pre_load = fdc_pre_load,
>      .post_load = fdc_post_load,
>      .fields = (VMStateField[]) {
>          /* Controller State */
> @@ -839,6 +919,9 @@ static const VMStateDescription vmstate_fdc = {
>              .vmsd = &vmstate_fdc_result_timer,
>              .needed = fdc_result_timer_needed,
>          } , {
> +            .vmsd = &vmstate_fdc_phase,
> +            .needed = fdc_phase_needed,
> +        } , {
>              /* empty */
>          }
>      }
> @@ -1137,6 +1220,7 @@ static uint32_t fdctrl_read_dir(FDCtrl *fdctrl)
>  /* Clear the FIFO and update the state for receiving the next command */
>  static void fdctrl_to_command_phase(FDCtrl *fdctrl)
>  {
> +    fdctrl->phase = FD_PHASE_COMMAND;
>      fdctrl->data_dir = FD_DIR_WRITE;
>      fdctrl->data_pos = 0;
>      fdctrl->msr &= ~(FD_MSR_CMDBUSY | FD_MSR_DIO);
> @@ -1146,6 +1230,7 @@ static void fdctrl_to_command_phase(FDCtrl *fdctrl)
>   * @fifo_len is the number of result bytes to be read out. */
>  static void fdctrl_to_result_phase(FDCtrl *fdctrl, int fifo_len)
>  {
> +    fdctrl->phase = FD_PHASE_RESULT;
>      fdctrl->data_dir = FD_DIR_READ;
>      fdctrl->data_len = fifo_len;
>      fdctrl->data_pos = 0;
> @@ -1912,6 +1997,9 @@ static void fdctrl_handle_relative_seek_out(FDCtrl *fdctrl, int direction)
>      fdctrl_raise_irq(fdctrl);
>  }
>  
> +/*
> + * Handlers for the execution phase of each command
> + */
>  static const struct {
>      uint8_t value;
>      uint8_t mask;
> @@ -2015,6 +2103,7 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value)
>          /* We now have all parameters
>           * and will be able to treat the command
>           */
> +        fdctrl->phase = FD_PHASE_EXECUTION;
>          if (fdctrl->data_state & FD_STATE_FORMAT) {
>              fdctrl_format_sector(fdctrl);
>              return;
> 

Acked-by: John Snow <jsnow@redhat.com>

Looks ok to me, CC David Gilbert for a migration look-see.

--js