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 > > CONFIG_MALLOC_UPPERMEMORY when building a CSM. > > 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 published. 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). -- dwmw2
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