Re: [Qemu-devel] OVMF Google Summer of Code ideas

[Jordan Justen]

On Tue, Mar 8, 2011 at 18:23, Kevin O'Connor <address@hidden> wrote:
> On Tue, Mar 08, 2011 at 09:00:05AM -0800, Jordan Justen wrote:
>> Yes, the UEFI system is still in place.  The UEFI part still handles
>> the majority of platform init, and calls into the CSM at various
>> points.  The CSM returns back to UEFI for all CSM calls, except the
>> legacy boot.
>
> Is there a concise list of these various callbacks between UEFI and
> CSM?
>
> If SeaBIOS just needs to be loaded up for legacy boots, that doesn't
> sound too difficult.  However, if SeaBIOS would need to translate
> various BIOS calls into UEFI calls - that sounds like it could be
> complex.

A CSM does not really know about UEFI for the most part.  Rather it
carries out some tasks when request by the UEFI environment.  The UEFI
side still manages the high level boot flow (even for legacy boots).
The CSM does not call into UEFI services, but just returns back to
whoever invoked the CSM call.

The 16-bit CSM component interface is described in this file:
https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/IntelFrameworkPkg/Include/Protocol/LegacyBios.h

The full CSM specification document is available here:
http://www.intel.com/technology/framework/spec.htm

Thanks,

-Jordan