[SeaBIOS] A question on SeaBIOS PCI Enumeration

[Prasad Joshi]

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
 #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?

>
> -Kevin
>