On Thu, 28 Jul 2022 13:29:07 +0100 Peter Maydell <peter.mayd...@linaro.org> 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 > > > --- > > 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...) unfortunately new features still creep in 'pc' machine ex: "acpi-root-pci-hotplug"), and I don't see an easy way to compile that nor enforce that in the future. Far from easy would be split piix4_pm on base/enhanced classes so we wouldn't need x86 specific hacks in 'base' variant (assuming 'enhanced' could maintain the current VMSTATE to keep cross-version migration working). > > +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 >