Re: [Qemu-devel] Re: qdev property bug?

[Anthony Liguori <anthony@codemonkey.ws>]

Sebastian Herbszt wrote:
> Anthony Liguori wrote:
>> Michael S. Tsirkin wrote:
>>> On Mon, Dec 14, 2009 at 02:43:38PM -0600, Anthony Liguori wrote:
>>>  
>>>> Because it can be selected by the user via the menu and because it 
>>>> can  be selected at runtime via the boot_set monitor command.
>>>>     
>>>
>>> Yes, but it's not like we have nowhere to store them.
>>> We could shadow ROM when it is actually needed.
>>>   
>>
>> I believe the way this works with real BIOSes is that the rom is 
>> initially loaded somewhere outside of the 1M region and it's init is 
>> executed.  It's then the rom's job to execute it's initialization.  
>> Afterwards, the bios copies the rom into the 1M region.  This is how 
>> PMM works.
>>
>> The idea is that while outside of the 1M region, the rom can 
>> eliminate unnecessary code and update it's own header to reflect it's 
>> new, improved code size. 
>
> It's more like the following (pci 2.2):
> - enable and map expansion rom bar
> - find rom and copy to ram (0xC000-0xDFFFF)
> - disable expansion rom bar
> - call rom init
> - rom might resize itself (DDIM)
> - write protect rom
>
> PMM doesn't have (anything?) to do with this and the rom doesn't have 
> to be loaded
> outside of 1MB.

Well PMM is used to do the resizing.

But it sounds like the problem is that we should not be loading the roms 
into the rom space.  Instead, seabios should be mapping them into that 
space, running the rom init, then moving to the next one.

I suspect we need to either need to implement the proper pci interface 
for seabios to do this or we need to provide a pv channel.

Regards,

Anthony Liguori