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

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Igor Mammedov (imammedo@redhat.com) wrote:
> On Thu, 28 Jul 2022 15:44:20 +0100
> "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?
> 
> Not sure what "'stub' vmsd" is, can you explain?

In hw/acpi/acpi-pci-hotplug-stub.c there is :
const VMStateDescription vmstate_acpi_pcihp_pci_status;

this seg happens when the migration code walks into that - this should
always get populated with some of the minimal fields, in particular the
.name and .fields array terminated with VMSTATE_END_OF_LIST().

Dave

> > 
> > Dave
> > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > ---
> > > 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" },
> > > +};
> > > +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
> > >   
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK