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Re: [PATCH for-7.1] hw/mips/malta: turn off x86 specific features of PII
From: |
Igor Mammedov |
Subject: |
Re: [PATCH for-7.1] hw/mips/malta: turn off x86 specific features of PIIX4_PM |
Date: |
Fri, 29 Jul 2022 10:09:49 +0200 |
On Thu, 28 Jul 2022 16:04:58 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:
> 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
it's not limited to VMSTATE_PCI_HOTPLUG but also memory hotplug
and other x86 specific knobs that may cause crash.
(I ignored cpu hotplug one for now since it doesn't cause crash)
>
> -- PMM
>