Re: [PATCH-for-8.2 v4 09/10] hw/char/pl011: Add transmit FIFO to PL011State

[Philippe Mathieu-Daudé]

On 16/11/23 16:48, Juan Quintela wrote:
> Richard Henderson <richard.henderson@linaro.org> wrote:
> > On 11/9/23 11:28, Philippe Mathieu-Daudé wrote:
> > > @@ -436,6 +438,24 @@ static const VMStateDescription vmstate_pl011_clock = {
> > >        }
> > >    };
> > >    +static bool pl011_xmit_fifo_state_needed(void *opaque)
> > > +{
> > > +    PL011State* s = opaque;
> > > +
> > > +    return !fifo8_is_empty(&s->xmit_fifo);
> > > +}
> > > +
> > > +static const VMStateDescription vmstate_pl011_xmit_fifo = {
> > > +    .name = "pl011/xmit_fifo",
> > > +    .version_id = 1,
> > > +    .minimum_version_id = 1,
> > > +    .needed = pl011_xmit_fifo_state_needed,
> > > +    .fields = (VMStateField[]) {
> > > +        VMSTATE_FIFO8(xmit_fifo, PL011State),
> > > +        VMSTATE_END_OF_LIST()
> > > +    }
> > > +};
> > > +
> > >    static int pl011_post_load(void *opaque, int version_id)
> > >    {
> > >        PL011State* s = opaque;
> > > @@ -487,7 +507,11 @@ static const VMStateDescription vmstate_pl011 = {
> > >        .subsections = (const VMStateDescription * []) {
> > >            &vmstate_pl011_clock,
> > >            NULL
> > > -    }
> > > +    },
> > > +    .subsections = (const VMStateDescription * []) {
> > > +        &vmstate_pl011_xmit_fifo,
> > > +        NULL
> > > +    },
> > >    };
> >
> > It just occurred to me that you may need a vmstate_pl011 pre_load() to
> > empty the FIFO, which will then be filled if and only if the saved
> > vmstate_pl011_xmit_fifo subsection is present.
> >
> > Juan, have I got this correct about how migration would or should handle a 
> > missing subsection?
>
> I hav'nt looked about how the device is created. But if it is created
> with the fifo empty you don't need the pre_load().

This is indeed the case. Thank you Juan!