Re: [PATCH for-7.1] hw/mips/malta: turn off x86 specific features of PIIX4_PM

[Peter Maydell]

On Thu, 28 Jul 2022 at 15:44, Dr. David Alan Gilbert
<dgilbert@redhat.com> wrote:
>
> * Igor Mammedov (imammedo@redhat.com) wrote:
> > QEMU crashes trying to save VMSTATE when only MIPS target are compiled in
> >   $ qemu-system-mips -monitor stdio
> >   (qemu) migrate "exec:gzip -c > STATEFILE.gz"
> >   Segmentation fault (core dumped)
> >
> > It happens due to PIIX4_PM trying to parse hotplug vmstate structures
> > which are valid only for x86 and not for MIPS (as it requires ACPI
> > tables support which is not existent for ithe later)
> >
> > Issue was probably exposed by trying to cleanup/compile out unused
> > ACPI bits from MIPS target (but forgetting about migration bits).
> >
> > Disable compiled out features using compat properties as the least
> > risky way to deal with issue.
>
> Isn't the problem partially due to a 'stub' vmsd which isn't terminated?

Yes, but setting these properties causes that vmsd
(vmstate_acpi_pcihp_pci_status) to not be used:

 * it is used only in VMSTATE_PCI_HOTPLUG()
 * that macro is used only in hw/acpi/ich9.c (not relevant here) and
   hw/acpi/piix4.c
 * in piix4.c it is invoked passing it the test functions
   vmstate_test_use_acpi_hotplug_bridge and
   vmstate_test_migrate_acpi_index
 * setting the properties on the device as this patch does
   causes those test functions to return false, so the
   vmstate_acpi_pcihp_pci_status is never examined

-- PMM