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
