Re: [PATCH v2] acpi: fix acpi_index migration

[Peter Maydell]

On Wed, 6 Apr 2022 at 19:59, Dr. David Alan Gilbert <dgilbert@redhat.com> wrote:
>
> * Igor Mammedov (imammedo@redhat.com) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > vmstate_acpi_pcihp_use_acpi_index() was expecting AcpiPciHpState
> > as state but it actually received PIIX4PMState, because
> > VMSTATE_PCI_HOTPLUG is a macro and not another struct.
> > So it ended up accessing random pointer, which resulted
> > in 'false' return value and acpi_index field wasn't ever
> > sent.
> >
> > However in 7.0 that pointer de-references to value > 0, and
> > destination QEMU starts to expect the field which isn't
> > sent in migratioon stream from older QEMU (6.2 and older).
> > As result migration fails with:
> >   qemu-system-x86_64: Missing section footer for 0000:00:01.3/piix4_pm
> >   qemu-system-x86_64: load of migration failed: Invalid argument
> >
> > In addition with QEMU-6.2, destination due to not expected
> > state, also never expects the acpi_index field in migration
> > stream.
> >
> > Q35 is not affected as it always sends/expects the field as
> > long as acpi based PCI hotplug is enabled.
> >
> > Fix issue by introducing compat knob to never send/expect
> > acpi_index in migration stream for 6.2 and older PC machine
> > types and always send it for 7.0 and newer PC machine types.
> >
> > Diagnosed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Fixes: b32bd76 ("pci: introduce acpi-index property for PCI device")
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/932
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Applied to master for rc3, thanks.

-- PMM