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

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

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!