[SeaBIOS] [PATCH v2] Update EFI_COMPATIBILITY16_TABLE to match 0.98 spec update

David Woodhouse dwmw2 at infradead.org
Mon May 19 20:34:45 CEST 2014

On Fri, 2014-01-10 at 12:49 -0500, Kevin O'Connor wrote:
> On Fri, Dec 06, 2013 at 11:56:22AM +0000, David Woodhouse wrote:
> > We expect to use the space between the top of option ROMs and the bottom
> > of our own BIOS code as a stack. OVMF was previously marking the whole
> > region from 0xC0000 to 0xFFFFF read-only before invoking our Legacy16Boot
> > method. Read-only stack considered harmful.
> > 
> > Version 0.98 of the CSM spec adds the UmaAddress and UmaSize fields, which
> > allow the CSM to specify a memory region that needs to be writable.
> > 
> > There exists CONFIG_MALLOC_UPPERMEMORY which we could turn off to use
> > the 9-segment, but that isn't particularly useful for the CSM case
> > either because that memory isn't ours to play with until the final
> > Legacy16Boot call. There's a LowPmmMemory given to use by UEFI to play
> > with, but that's right in the *middle* of low memory and using that for
> > persistent allocations would be painful. So just require
> Hi David,
> Are you still looking at this?  If I recall correctly, you were going
> to run a test without CONFIG_MALLOC_UPPERMEMORY set.

Apologies for the sporadic nature of my attention to this. It's back at
the top of my pile again for a while. I've submitted the corresponding
patch to EDK2 and it should hopefully be accepted now that the spec is

As I'm testing on Quark today, I tried reverting the EDK2-side patch and
the SeaBIOS patch, and disabling CONFIG_MALLOC_UPPERMEMORY. It booted
FreeDOS and worked fine.

Then I re-enabled CONFIG_MALLOC_UPPERMEMORY and it still worked, which
wasn't expected :)

I'll have to retest with OVMF under Qemu (with KVM).


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