Re: [Qemu-devel] Memory API: handling unassigned physical memory

[Avi Kivity]

On 05/01/2012 05:15 PM, Anthony Liguori wrote:
>>> I think a nice fix would be to make it_shift as memory region mutator
>>> and allow it to be set after initialization.
>>
>> Indeed I wanted to make it_shift as part of the memory core.  But a
>> mutator?  It doesn't change in real hardware, so this looks artificial.
>> So far all mutators really change at runtime.
>
>
> QOM has a concept of initialization and realize.  You can change
> properties after initialization but not before realize.
>
> So as long as it_shift can be set after initialization but before
> realize (which I think is roughly memory_region_add_subregion) it
> doesn't need to be a mutator.

Ok, good.

>
>> What is the problem with delaying region initialization until realize?
>
> We need to initialize the MemoryRegion in order to expose it as a
> property.  We want to do that during initialize.  Here's an example:
>
> qom-create isa-i8259 foo
> qom-set /peripheral/foo/io it_shift 1
> qom-set /peripheral/foo/realize true
>
> For this to work, it_shift needs to be a QOM property of the "io"
> MemoryRegion.  The MemoryRegion needs to be created in instance_init.

So it looks like we need two phase initialization for memory regions as
well?

Not so pretty.

>
>>> b) There's some duplication in MemoryRegions with respect to QOM.
>>> Memory regions want to have a name but with QOM they'll be addressable
>>> via a path.  I go back and forth about how aggressively we want to
>>> refactor MemoryRegions.
>>
>> These days region names are purely for debugging.  The ABI bit was moved
>> to a separate function.
>
> Fair enough.
>
> BTW, in the branch I've posted, I've got a number of memory API
> conversions or removal of legacy interfaces.

Nice.  But you use get_system_io(), which is bad.

-- 
error compiling committee.c: too many arguments to function