On Thu, 28 Jul 2022, Peter Maydell wrote:
> On Thu, 28 Jul 2022 at 12:50, Igor Mammedov <imamm...@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.
> >
> > Signed-off-by: Igor Mammedov <imamm...@redhat.com>
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/995
Reviewed-by: Ani Sinha <a...@anisinha.ca>
>
> > ---
> > PS:
> > another approach could be setting defaults to disabled state and
> > enabling them using compat props on PC machines (which is more
> > code to deal with => more risky) or continue with PIIX4_PM
> > refactoring to split x86-shism out (which I'm not really
> > interested in due to risk of regressions for not much of
> > benefit)
> > ---
> > hw/mips/malta.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/hw/mips/malta.c b/hw/mips/malta.c
> > index 7a0ec513b0..0e932988e0 100644
> > --- a/hw/mips/malta.c
> > +++ b/hw/mips/malta.c
> > @@ -1442,6 +1442,14 @@ static const TypeInfo mips_malta_device = {
> > .instance_init = mips_malta_instance_init,
> > };
> >
> > +GlobalProperty malta_compat[] = {
> > + { "PIIX4_PM", "memory-hotplug-support", "off" },
> > + { "PIIX4_PM", "acpi-pci-hotplug-with-bridge-support", "off" },
> > + { "PIIX4_PM", "acpi-root-pci-hotplug", "off" },
> > + { "PIIX4_PM", "x-not-migrate-acpi-index", "true" },
> > +};
>
> Is there an easy way to assert in hw/acpi/piix4.c that if
> CONFIG_ACPI_PCIHP was not set then the board has initialized
> all these properties to the don't-use-hotplug state ?
> That would be a guard against similar bugs (though I suppose
> we probably aren't likely to add new piix4 boards...)
>
> > +const size_t malta_compat_len = G_N_ELEMENTS(malta_compat);
> > +
> > static void mips_malta_machine_init(MachineClass *mc)
> > {
> > mc->desc = "MIPS Malta Core LV";
> > @@ -1455,6 +1463,7 @@ static void mips_malta_machine_init(MachineClass *mc)
> > mc->default_cpu_type = MIPS_CPU_TYPE_NAME("24Kf");
> > #endif
> > mc->default_ram_id = "mips_malta.ram";
> > + compat_props_add(mc->compat_props, malta_compat, malta_compat_len);
> > }
> >
> > DEFINE_MACHINE("malta", mips_malta_machine_init)
> > --
> > 2.31.1
>
> thanks
> -- PMM
>
