On Jan 29, 2013, at 1:45 PM, Kevin OConnor <ke...@koconnor.net> wrote:
> I'm a bit surprised that OVMF would mark all of the 0xc0000-0xfffff
> area as read-only. There are lots of old programs that want to use
> parts of that area as memory.
Kevin,
This was all a long time ago, and my memory is fuzzy on things 16-bits ....
It looks like generic CSM code locks the 0xC0000 - 0xFFFFF region prior to
boot, and I seem to remember that this was the common practice at the time. I'm
not sure what old programs you are talking about, but I think they would not
run on lots of PCs from the last decade+.
All the OVMF does is abstract the 440 PAM registers via the
EFI_LEGACY_REGION2_PROTOCOL. While it is not an ideal solution this code could
be updated to lie and not lock a range that the SeaBIOS could use. Looks like
the PAM registers can lock the E segment in 16K chunks, so you can just pick a
range to reserve for the SeaBIOS and update the OVMF code here
https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/OvmfPkg/Csm/CsmSupportLib/LegacyRegion.c.
Thanks,
Andrew Fish
.
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