Re: [Qemu-devel] [RFC 01/18] pc: create "PC" device class

[Eduardo Habkost]

On Thu, Oct 04, 2012 at 08:46:46AM -0500, Anthony Liguori wrote:
> Eduardo Habkost <address@hidden> writes:
> 
> > We can make it a child of a generic "machine" class later, but right now
> > a "PC" class is needed to allow global-properties to control some
> > details of CPU creation on the PC code.
> >
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  hw/pc.c | 18 ++++++++++++++++++
> >  hw/pc.h |  6 ++++++
> >  2 files changed, 24 insertions(+)
> >
> > diff --git a/hw/pc.c b/hw/pc.c
> > index 7e7e0e2..9b68282 100644
> > --- a/hw/pc.c
> > +++ b/hw/pc.c
> > @@ -550,6 +550,24 @@ static void bochs_bios_write(void *opaque, uint32_t 
> > addr, uint32_t val)
> >      }
> >  }
> >  
> > +typedef struct PC {
> > +    DeviceState parent_obj;
> > +} PC;
> 
> So the general problem with this approach is that it strays from
> modeling hardware.

True, it's not modelling hardware. It's controlling the behavior of the
QEMU code that set APIC IDs, because we need to keep the old behavior on
old machine-types.

> 
> I guess I'm confused why we're not just adding an apic_id property to
> the CPU objects and setting that via the normal QOM accessors.
> 
> Wouldn't that solve the problem?
> 

It wouldn't solve the problem (although it can make the code look
better).

The problem is not setting the APIC ID, is controlling the code that
generates the APIC IDs. I don't care too much where that code would live
(it could be inside cpu.c or helper.c), but it still needs a flag where
old machine-types tell it "please keep the old behavior for
compatibility".


> Regards,
> 
> Anthony Liguori
> 
> > +
> > +static const TypeInfo pc_type_info = {
> > +    .name = TYPE_PC_MACHINE,
> > +    .parent = TYPE_DEVICE,
> > +    .instance_size = sizeof(PC),
> > +    .class_size = sizeof(DeviceClass),
> > +};
> > +
> > +static void pc_register_type(void)
> > +{
> > +    type_register_static(&pc_type_info);
> > +}
> > +
> > +type_init(pc_register_type);
> > +
> >  int e820_add_entry(uint64_t address, uint64_t length, uint32_t type)
> >  {
> >      int index = le32_to_cpu(e820_table.count);
> > diff --git a/hw/pc.h b/hw/pc.h
> > index e4db071..77e898f 100644
> > --- a/hw/pc.h
> > +++ b/hw/pc.h
> > @@ -102,6 +102,12 @@ void i8042_setup_a20_line(ISADevice *dev, qemu_irq 
> > *a20_out);
> >  /* pc.c */
> >  extern int fd_bootchk;
> >  
> > +#define TYPE_PC_MACHINE "PC"
> > +#define PC(obj) \
> > +    OBJECT_CHECK(PC, (obj), TYPE_PC_MACHINE)
> > +struct PC;
> > +typedef struct PC PC;
> > +
> >  void pc_register_ferr_irq(qemu_irq irq);
> >  void pc_acpi_smi_interrupt(void *opaque, int irq, int level);
> >  
> > -- 
> > 1.7.11.4

-- 
Eduardo