From c0a2284d858d463ec11597815d542d11fceac768 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Fri, 8 Feb 2013 15:52:01 +0000 Subject: [PATCH] Add README.CSM Signed-off-by: David Woodhouse --- README.CSM | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) create mode 100644 README.CSM diff --git a/README.CSM b/README.CSM new file mode 100644 index 0000000..ea71846 --- /dev/null +++ b/README.CSM @@ -0,0 +1,21 @@ +Enabling CONFIG_CSM allows SeaBIOS to be built as a Compatibility Support +Module for use with the OMVF/EDK-II UEFI firmware. + +It will provide "legacy" BIOS services for booting non-EFI operating +systems and will also allow OVMF to display on otherwise unsupported +video hardware by using the traditional VGA BIOS. + +Windows 2008r2 is known to use INT 10h BIOS calls even when booted via +EFI, and the presence of a CSM makes this work as expected too. + +Having built SeaBIOS with CONFIG_CSM, you should be able to drop the +result into your OVMF build tree at OvmfPkg/Csm/Csm16/Csm16.bin and +then build OVMF with 'build -D CSM_ENABLE'. The SeaBIOS binary will be +included as a discrete file within the 'Flash Volume' which is +created, and there are tools which will extract it and allow it to be +replaced; satisfying the requirements of the LGPL licence. + +A patch to OVMF is required, to prevent it from marking the region from +0xC0000-0xFFFFF as read-only before invoking our Legacy16Boot method. See +http://www.sourceforge.net/mailarchive/forum.php?thread_name=50FD7290.9060003%40redhat.com&forum_name=edk2-devel + -- 2.39.5