Re: [PATCH v3 05/11] pckbd: don't update OBF flags if KBD_STAT_OBF is set

[Volker Rümelin]

>    Hi,
>
> >   static const VMStateDescription vmstate_kbd = {
> >       .name = "pckbd",
> > -    .version_id = 3,
> > +    .version_id = 4,
> >       .minimum_version_id = 3,
> >       .post_load = kbd_post_load,
> >       .fields = (VMStateField[]) {
> > @@ -435,6 +471,7 @@ static const VMStateDescription vmstate_kbd = {
> >           VMSTATE_UINT8(status, KBDState),
> >           VMSTATE_UINT8(mode, KBDState),
> >           VMSTATE_UINT8(pending, KBDState),
> > +        VMSTATE_UINT8_V(obdata, KBDState, 4),
> >           VMSTATE_END_OF_LIST()
> >       },
> >       .subsections = (const VMStateDescription*[]) {
> > @@ -512,12 +549,20 @@ void i8042_setup_a20_line(ISADevice *dev, qemu_irq 
> > a20_out)
> >       qdev_connect_gpio_out_named(DEVICE(dev), I8042_A20_LINE, 0, a20_out);
> >   }
> Unfortunately live migration isn't that easy.  Reason is we want able to
> live-migrate both ways (old qemu -> new qemu but also new qemu -> old qemu).
> With version ids we can do old qemu -> new qemu only.
>
> So the usual way to deal with this is that new features which require
> additional state information can be enabled/disabled at runtime using
> device properties.  The feature is turned off for the compatibility
> machine types.  The additional state is added using a conditional
> subsection, which is only sent in case the feature is enabled.  That way
> qemu with -- says -- "-machine pc-q35-5.0" will only enable features and
> sent vmstate which qemu 5.0 is able to deal with.
>
> I think there is no way around such a property for the ps2 fixes, even
> if we use it for sending/not sending the additional ps2 state
> information needed by the bugfixes.  Making the fixes itself conditional
> should not be needed I think.

Thank you for the detailed information. This is really helpful.
I will send a version 4 series. It may take a few days.

With best regards,
Volker

> take care,
>    Gerd