Re: [Qemu-arm] [PATCH 23/27] hw/core/or-irq: Support more than 16 inputs to an OR gate

[Paolo Bonzini]

On 21/05/2018 16:03, Peter Maydell wrote:
> + * VMState array; devices with more inputs than this need to
> + * migrate the extra lines via a subsection.
> + * The subsection migrates as much of the levels[] array as is needed
> + * (including repeating the first 16 elements), to avoid the awkwardness
> + * of splitting it in two to meet the requirements of VMSTATE_VARRAY_UINT16.
> + */
> +#define OLD_MAX_OR_LINES 16
> +#if MAX_OR_LINES < OLD_MAX_OR_LINES
> +#error MAX_OR_LINES must be at least 16 for migration compatibility
> +#endif
> +
> +static bool vmstate_extras_needed(void *opaque)
> +{
> +    qemu_or_irq *s = OR_IRQ(opaque);
> +
> +    return s->num_lines >= OLD_MAX_OR_LINES;
> +}
> +
> +static const VMStateDescription vmstate_or_irq_extras = {
> +    .name = "or-irq-extras",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = vmstate_extras_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_VARRAY_UINT16_UNSAFE(levels, qemu_or_irq, num_lines, 0,
> +                                     vmstate_info_bool, bool),
> +        VMSTATE_END_OF_LIST(),
> +    },
> +};
> +


Why do the levels have to be migrated at all?  It should be enough if
the IRQ level is either migrated manually, or restored (e.g. in
post_save callbacks) through other data that is migrated.

Paolo