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David Woodhousec0a22842013-02-08 15:52:01 +00001Enabling CONFIG_CSM allows SeaBIOS to be built as a Compatibility Support
2Module for use with the OMVF/EDK-II UEFI firmware.
4It will provide "legacy" BIOS services for booting non-EFI operating
5systems and will also allow OVMF to display on otherwise unsupported
6video hardware by using the traditional VGA BIOS.
8Windows 2008r2 is known to use INT 10h BIOS calls even when booted via
9EFI, and the presence of a CSM makes this work as expected too.
11Having built SeaBIOS with CONFIG_CSM, you should be able to drop the
12result into your OVMF build tree at OvmfPkg/Csm/Csm16/Csm16.bin and
13then build OVMF with 'build -D CSM_ENABLE'. The SeaBIOS binary will be
14included as a discrete file within the 'Flash Volume' which is
15created, and there are tools which will extract it and allow it to be
16replaced; satisfying the requirements of the LGPL licence.
18A patch to OVMF is required, to prevent it from marking the region from
190xC0000-0xFFFFF as read-only before invoking our Legacy16Boot method. See