[SeaBIOS] [PATCH] mark VBE mapping as reserved in e820

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sun Jan 24 15:26:55 CET 2010

Hi Izik,

On 24.01.2010 00:35, Izik Eidus wrote:
> To make life easier for us we can look on the acpi spec (3b) that say:
> 14.5 Example Address Map
> This sample address map (for an Intel processor-based system) describes a machine that has 128 MB of
> RAM, 640 KB of base memory and 127 MB of extended memory. The base memory has 639 KB available
> for the user and 1 KB for an extended BIOS data area. A 4-MB Linear Frame Buffer (LFB) is based at 12
> MB. The memory hole created by the chip set is from 8 MB to 16 MB. Memory-mapped APIC devices are
> in the system. The I/O Unit is at FEC00000 and the Local Unit is at FEE00000. The system BIOS is
> remapped to 1 GB–64 KB.

The sentence above is a bug in the spec. The system BIOS is remapped to
4 GB - 64 kB (not 1 GB - 64 kB).

> The 639-KB endpoint of the first memory range is also the base memory size reported in the BIOS data
> segment at 40:13. The following table shows the memory map of a typical system.
>                                     Table 14-8 Sample Memory Map
>   Base (Hex)      Length     Type                      Description
>   0000 0000       639 KB     AddressRangeMemory        Available Base memory. Typically the same value
>                                                        as is returned using the INT 12 function.
>                            Hewlett-Packard/Intel/Microsoft/Phoenix/Toshiba
>                                                   System Address Map Interfaces 399
> Base (Hex) Length Type                 Description
> 0009 FC00  1 KB   AddressRangeReserved Memory reserved for use by the BIOS(s). This
>                                        area typically includes the Extended BIOS data
>                                        area.
> 000F 0000  64 KB  AddressRangeReserved System BIOS
> 0010 0000  7 MB   AddressRangeMemory   Extended memory, which is not limited to the
>                                        64-MB address range.
> 0080 0000  4 MB   AddressRangeReserved Chip set memory hole required to support the
>                                        LFB mapping at 12 MB.
> 0100 0000  120 MB AddressRangeMemory   Baseboard RAM relocated above a chip set
>                                        memory hole.
> FEC0 0000  4 KB   AddressRangeReserved I/O APIC memory mapped I/O at FEC00000.
> FEE0 0000  4 KB   AddressRangeReserved Local APIC memory mapped I/O at FEE00000.
> FFFF 0000  64 KB  AddressRangeReserved Remapped System BIOS at end of address space.
> So we can see that even the acpi spec example mark the LFB region as reserved.

No, the memory hole is marked as reserved. The LFB region is not listed


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"We are juggling too many chainsaws and flaming arrows and tigers."

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