Re: [Qemu-devel] [RFC] Memory API

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-05-19 13:57, Avi Kivity wrote:
> On 05/19/2011 02:54 PM, Gleb Natapov wrote:
>>>
>>>  In this case the device would call a chipset function, passing the
>>>  memory region as a parameter, and the chipset would call
>>>  m_r_add_subregion().
>> But then chipset can resolve all overlapping by itself and register only
>> regions that are actually accessible by a guest software.
> 
> Sure it can (and it does now), but it's hard.  This API centralizes the 
> logic, leaving the devices/chipsets to specify what they want.
> 
> For a PC, we have at least two such cases, the ISA bus and the PCI bus.
> 
>>   Also there are
>> devices that on some architectures are accessed through a chipset and on
>> other they resides directly on a system bus. If they will need to call
>> different memory registration api depending on how they are instantiated
>> the code can become messy.
> 
> An example is ne2000-isa and ne2000-pci.  There's no getting around some 
> glue logic, but I think this API minimizes it (you can declare 
> everything about your memory region in common code, the only thing that 
> is different is registration).

If devices register against the corresponding qbus (I expect we'll have
multiple ones in the future), not even that need to be different.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux