[SeaBIOS] A question on SeaBIOS PCI Enumeration

[Kevin O'Connor]

On Thu, Feb 10, 2011 at 03:51:04PM +0000, Prasad Joshi wrote:
> Thanks a lot for your reply.
> 
> On Thu, Feb 10, 2011 at 3:31 PM, Kevin O'Connor <kevin at koconnor.net> wrote:
> > On Mon, Feb 07, 2011 at 07:17:52PM +0000, Prasad Joshi wrote:
> >> Hello,
> >>
> >>
> >> 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.
> 
> I modified the memory range according the lspci -vv output.
> Atleast on my machine, the memory range 0xf0000000 to 0xfec00000 is
> reserved for non-prefectable memory.
> 
> Here is a small modification. As long as it keeps the behavior for old
> pci assignments, I guess this would not be a problem.
> 
> diff --git a/src/config.h b/src/config.h
> index 5b40488..19729cb 100644
> --- a/src/config.h
> +++ b/src/config.h
> @@ -49,20 +49,18 @@
> 
>  // Support old pci mem assignment behaviour
>  //#define CONFIG_OLD_PCIMEM_ASSIGNMENT    1
> -#if CONFIG_OLD_PCIMEM_ASSIGNMENT
>  #define BUILD_PCIMEM_START        0xf0000000
>  #define BUILD_PCIMEM_SIZE         (BUILD_PCIMEM_END - BUILD_PCIMEM_START)
>  #define BUILD_PCIMEM_END          0xfec00000    /* IOAPIC is mapped at */
> +
> +#if CONFIG_OLD_PCIMEM_ASSIGNMENT
>  #define BUILD_PCIPREFMEM_START    0
>  #define BUILD_PCIPREFMEM_SIZE     0
>  #define BUILD_PCIPREFMEM_END      0
>  #else
> -#define BUILD_PCIMEM_START        0xf0000000
> -#define BUILD_PCIMEM_SIZE         0x08000000    /* half- of pci window */
> -#define BUILD_PCIMEM_END          (BUILD_PCIMEM_START + BUILD_PCIMEM_SIZE)
> -#define BUILD_PCIPREFMEM_START    BUILD_PCIMEM_END
> +#define BUILD_PCIPREFMEM_START    0xc0000000

As before, I believe real memory could be at 0xc0000000-0xe0000000, so
this range can't be used for PCI bars.


>  #define BUILD_PCIPREFMEM_SIZE     (BUILD_PCIPREFMEM_END -
> BUILD_PCIPREFMEM_START)
> -#define BUILD_PCIPREFMEM_END      0xfec00000    /* IOAPIC is mapped at */
> +#define BUILD_PCIPREFMEM_END      0xdfffffff
>  #endif
> 
>  #define BUILD_APIC_ADDR           0xfee00000
> 
> Also, in the function pci_bios_allocate_region(), discards the
> prefectable memory region and places it in the non-prefectable memory
> region, if the bus is 0.
> 
>          } else if ((val & PCI_BASE_ADDRESS_MEM_PREFETCH) &&
>                     /* keep behaviour on bus = 0 */
>                     pci_bdf_to_bus(bdf) != 0 &&
>                     /* If pci_bios_prefmem_addr == 0, keep old behaviour */
>                     pci_region_addr(&pci_bios_prefmem_region) != 0) {
> 
> I am not sure if this can be changed, can you please shade more light on this?

I think Isaku is more familiar with this code.

-Kevin