Re: [Qemu-devel] [RFC v2 00/20] Memory API

[Avi Kivity <avi@redhat.com>]

On 06/27/2011 04:21 PM, Avi Kivity wrote:
> As expected, this is taking longer than expected, so I'm releasing something
> less complete than I'd have liked.  Not even all of the PC machine is
> converted, but the difficult parts are (cirrus).  It appears to work well.
>
> The major change compared to v1 is the introduction of
> memory_region_init_alias(), which defines a memory region in terms of another.
> With the current API, the ability to alias is provided by address arithmetic
> on ram_addr_t:
>
>    ram_addr = qemu_ram_alloc(...);
>    cpu_register_physical_memory(..., ram_addr, size, ...);
>    /* alias: */
>    cpu_register_physical_memory(..., ram_addr + offset, another_size, ...);
>
> With the new API, you have to create an alias:
>
>    memory_region_init_ram(&mem, ...);
>    memory_region_register_subregion(...,&mem);
>    /* alias: */
>    memory_region_init_alias(&alias, ...,&mem, offset, another_size);
>    memory_region_register_subregion(...,&alias);
>
> The patchset is somewhat churny.  One of the reasons is that we move from a
> handle/pointer scheme in ram_addr_t to an object constructor/destructor scheme.
> Another is that region size becomes a property of a region instead of being
> maintained externally.  Also, container memory regions must be passed around,
> though we don't do that as well as we should.
>
> Todo:
>    - eliminate calls to get_system_memory() (where we ignore the bus hierarchy)
>    - add PCI APIs for the VGA window
>    - support the PIO address space using the memory API (allowing simplified
>      PCI BAR registration)
>    - convert 440FX
>    - convert everything else

Michael, I'm looking at the pci bridge code, and it basically does the 
same thing - clip each BAR to the intersection of the decode window of 
all bridges it hides behind.

How does a PCI bridge behave wrt VGA?  is it a separate control?  If so 
I probably need to implement generalized clipping (i.e. decode between 
0xa0000-0xc0000 or between 0xc0000000-0xf0000000).

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