Re: [PATCH v5 4/8] vt82c686: Introduce abstract TYPE_VIA_ISA and base vt82c686b_isa on it

[David Gibson]

On Thu, Mar 04, 2021 at 11:42:10PM +0100, Philippe Mathieu-Daudé wrote:
> On 3/4/21 9:16 PM, BALATON Zoltan wrote:
> > On Thu, 4 Mar 2021, Philippe Mathieu-Daudé wrote:
> >> On 3/2/21 10:11 PM, BALATON Zoltan wrote:
> >>> To allow reusing ISA bridge emulation for vt8231_isa move the device
> >>> state of vt82c686b_isa emulation in an abstract via_isa class.
> >>>
> >>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> >>> ---
> >>>  hw/isa/vt82c686.c        | 70 ++++++++++++++++++++++------------------
> >>>  include/hw/pci/pci_ids.h |  2 +-
> >>>  2 files changed, 40 insertions(+), 32 deletions(-)
> >>>
> >>> diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
> >>> index 72234bc4d1..5137f97f37 100644
> >>> --- a/hw/isa/vt82c686.c
> >>> +++ b/hw/isa/vt82c686.c
> >>> @@ -609,24 +609,48 @@ static const TypeInfo vt8231_superio_info = {
> >>>  };
> >>>
> >>>
> >>> -OBJECT_DECLARE_SIMPLE_TYPE(VT82C686BISAState, VT82C686B_ISA)
> >>> +#define TYPE_VIA_ISA "via-isa"
> >>> +OBJECT_DECLARE_SIMPLE_TYPE(ViaISAState, VIA_ISA)
> >>>
> >>> -struct VT82C686BISAState {
> >>> +struct ViaISAState {
> >>>      PCIDevice dev;
> >>>      qemu_irq cpu_intr;
> >>>      ViaSuperIOState *via_sio;
> >>>  };
> >>>
> >>> +static const VMStateDescription vmstate_via = {
> >>> +    .name = "via-isa",
> >>
> >> You changed the migration stream name, so I think we have
> >> a problem with migration... No clue how to do that properly.
> > 
> > I don't think these machines support migration or state description of
> > vt86c686b was not missing something before these patches that would make
> > it not work anyway so I did not worry about this too much. I doubt
> > anybody wants to migrate a fuloong2e machine so this should not be a
> > problem in practice but maybe you can mention it in the release notes if
> > you think that would be necessary.
> 
> Maybe just add in the description:
> 
>  This change breaks migration back compatibility, but
>  this is not an issue for the Fuloong2E machine.

Hrm.  If migration was never supported, why is there a vmstate
description there at all though?

That said, I don't think breaking compat is a problem: that's only an
issue where we actually have versioned machine types, which covers
only pc, pseries, arm virt and a very few others.  I don't think this
device was used on any of them.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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