[SeaBIOS] A question on SeaBIOS PCI Enumeration

[Kevin O'Connor]

On Mon, Feb 07, 2011 at 07:17:52PM +0000, Prasad Joshi wrote:
> Hello,
> 
> I am working on QEMU to pass-through a graphics device. I noticed few
> problems with PCI enumeration hence I compiled SeaBIOS with more debug
> information.
> 
> The PCI enumeration problem seems to be related to BUILS_PCIMEM_SIZE. I keep
> on getting the error 'increase BUILD_PCIMEM_SIZE and recompile'. This
> happens when BIOS tries to allocate 128MB for one of the BAR. The code seems
> to be printing the correct error as, the 128MB naturally aligned memory
> request can not be satisfied. No problem with this.
> 
> As I notice on my host machine the same case happens, but host BIOS seems to
> be allocating 128MB memory from some other region (c0000000-c7ffffff)
> 
[...]
> Can SeaBIOS do the same thing? or to put in other words Can SeaBIOS allocate
> memory from some other region instead of fixed f0000000 to (0xfec00000-1)?

It should be possible to alter BUILD_PCIMEM_START in src/config.h.
The reason it is at 0xf0000000 is because regular memory can go up to
0xe0000000, and the bochs vga bios had soe dependency on the address
space at 0xe0000000 - though this may no longer be the case.

-Kevin