Re: [Qemu-devel] [PATCH 07/10] serial: fixing vmstate for save/restore

[Juan Quintela <quintela@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> wrote:
> From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
>
> Some fields were added to VMState by this patch to preserve correct
> loading of the serial port controller state.
> Updating FCR value while loading was also modified to disable generating
> an interrupt by loadvm.
>
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/char/serial.c | 265 +++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 220 insertions(+), 45 deletions(-)
>
> diff --git a/hw/char/serial.c b/hw/char/serial.c
> index 764e184..2b04927 100644
> --- a/hw/char/serial.c
> +++ b/hw/char/serial.c
> @@ -272,6 +272,64 @@ static gboolean serial_xmit(GIOChannel *chan, GIOCondition cond, void *opaque)
>  }
>  
>  
> +/* Setter for FCR.
> +   is_load flag means, that value is set while loading VM state
> +   and interrupt should not be invoked */
> +static void serial_write_fcr(void *opaque, uint32_t val, int is_load)
> +{
> +    SerialState *s = opaque;

Both users call it with SerialState *s, not a void *.

is_load can be a bool.

> +static int serial_pre_load(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;

Unneeded cast (and not used in the rest of the file)


> +    s->thr_ipending = -1;
> +    s->poll_msl = -1;

We set both to -1.


> +    return 0;
> +}
> +
>  static int serial_post_load(void *opaque, int version_id)
>  {
>      SerialState *s = opaque;
> @@ -597,17 +620,139 @@ static int serial_post_load(void *opaque, int version_id)
>      if (version_id < 3) {
>          s->fcr_vmstate = 0;
>      }
> +    if (s->thr_ipending == -1) {
> +        s->thr_ipending = ((s->iir & UART_IIR_ID) == UART_IIR_THRI);
> +    }

If it is still -1 at this point, we "calculate" a value for it.
(I assume it is right, no knowledge of serial port)

But poll_msl is "more" interesting, because we are not "reseting it".

So, we have that if we are migrating from an old version, we would have
poll_msl == -1, and we used to have it to poll_msl == 0.

Should we change it?

I think that putting:

s->poll_msl = 0;

in preload, and 

static bool serial_poll_needed(void *opaque)
{
    SerialState *s = opaque;
    return s->poll_msl != 0;
}

would give exactly the same behaviour for new qemus, and behave better
for older ones?

what do you think?

Later, Juan.



> +    s->last_break_enable = (s->lcr >> 6) & 1;
>      /* Initialize fcr via setter to perform essential side-effects */
> -    serial_ioport_write(s, 0x02, s->fcr_vmstate, 1);
> +    serial_write_fcr(s, s->fcr_vmstate, 1);
>      serial_update_parameters(s);
>      return 0;
>  }
>  
> +static bool serial_thr_ipending_needed(void *opaque)
> +{
> +    SerialState *s = opaque;
> +    bool expected_value = ((s->iir & UART_IIR_ID) == UART_IIR_THRI);
> +    return s->thr_ipending != expected_value;
> +}
> +
> +const VMStateDescription vmstate_serial_thr_ipending = {
> +    .name = "serial/thr_ipending",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_INT32(thr_ipending, SerialState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_tsr_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return s->tsr_retry != 0;
> +}
> +
> +const VMStateDescription vmstate_serial_tsr = {
> +    .name = "serial/tsr",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_INT32(tsr_retry, SerialState),
> +        VMSTATE_UINT8(thr, SerialState),
> +        VMSTATE_UINT8(tsr, SerialState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_recv_fifo_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return !fifo8_is_empty(&s->recv_fifo);
> +
> +}
> +
> +const VMStateDescription vmstate_serial_recv_fifo = {
> +    .name = "serial/recv_fifo",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_STRUCT(recv_fifo, SerialState, 1, vmstate_fifo8, Fifo8),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_xmit_fifo_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return !fifo8_is_empty(&s->xmit_fifo);
> +}
> +
> +const VMStateDescription vmstate_serial_xmit_fifo = {
> +    .name = "serial/xmit_fifo",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_STRUCT(xmit_fifo, SerialState, 1, vmstate_fifo8, Fifo8),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_fifo_timeout_timer_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return timer_pending(s->fifo_timeout_timer);
> +}
> +
> +const VMStateDescription vmstate_serial_fifo_timeout_timer = {
> +    .name = "serial/fifo_timeout_timer",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_TIMER(fifo_timeout_timer, SerialState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_timeout_ipending_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return s->timeout_ipending != 0;
> +}
> +
> +const VMStateDescription vmstate_serial_timeout_ipending = {
> +    .name = "serial/timeout_ipending",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_INT32(timeout_ipending, SerialState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool serial_poll_needed(void *opaque)
> +{
> +    SerialState *s = (SerialState *)opaque;
> +    return s->poll_msl >= 0;
> +}
> +
> +const VMStateDescription vmstate_serial_poll = {
> +    .name = "serial/poll",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_INT32(poll_msl, SerialState),
> +        VMSTATE_TIMER(modem_status_poll, SerialState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  const VMStateDescription vmstate_serial = {
>      .name = "serial",
>      .version_id = 3,
>      .minimum_version_id = 2,
>      .pre_save = serial_pre_save,
> +    .pre_load = serial_pre_load,
>      .post_load = serial_post_load,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT16_V(divider, SerialState, 2),
> @@ -621,6 +766,32 @@ const VMStateDescription vmstate_serial = {
>          VMSTATE_UINT8(scr, SerialState),
>          VMSTATE_UINT8_V(fcr_vmstate, SerialState, 3),
>          VMSTATE_END_OF_LIST()
> +    },
> +    .subsections = (VMStateSubsection[]) {
> +        {
> +            .vmsd = &vmstate_serial_thr_ipending,
> +            .needed = &serial_thr_ipending_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_tsr,
> +            .needed = &serial_tsr_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_recv_fifo,
> +            .needed = &serial_recv_fifo_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_xmit_fifo,
> +            .needed = &serial_xmit_fifo_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_fifo_timeout_timer,
> +            .needed = &serial_fifo_timeout_timer_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_timeout_ipending,
> +            .needed = &serial_timeout_ipending_needed,
> +        } , {
> +            .vmsd = &vmstate_serial_poll,
> +            .needed = &serial_poll_needed,
> +        } , {
> +            /* empty */
> +        }
>      }
>  };
>  
> @@ -642,6 +813,10 @@ static void serial_reset(void *opaque)
>      s->char_transmit_time = (get_ticks_per_sec() / 9600) * 10;
>      s->poll_msl = 0;
>  
> +    s->timeout_ipending = 0;
> +    timer_del(s->fifo_timeout_timer);
> +    timer_del(s->modem_status_poll);
> +
>      fifo8_reset(&s->recv_fifo);
>      fifo8_reset(&s->xmit_fifo);