RAM1 stage: Since some RAM Physical mapping (AFTER *CRB*) MUST be done at
the
beginning of the RAM stage, lookalike BIOS one (in PEI phase, I assume),
CB will proceed
with the usual activities, set in Protected Mode. And, as we know so far
how it works, it'll
finish this phase, looking for Payload.
Meant *MRC* (Memory Reference Code), but for some reason wrote CRB??? These damned INTEL abbreviations will kill me...Indeed?!
On Sat, Aug 5, 2017 at 7:12 PM, ron minnich rminnich@gmail.com wrote:
in the akaros virtual machine code, we set up a simple 1:1 map and start linux at the 64-bit entry point, at which point it builds its own page tables. So entering a payload in long mode is certainly possible and IMHO ought to be the standard on amd64 -- not that anyone cares what I think anyway :-)
Anyway, I'm going to be working on replacing ramstage with linux again, so I'm not as concerted with coreboot ramstage just now ;-)
YUP, understood. You have to have RAM stage (before Linux), where you'll do the first 4GB of Physical Memory Mapping (you know, MTRR init and such kind of work), but as I see you'll try to make minimization of it:
[image: Inline image 1]
Anyway, after this you must do table init since you are, after all, switching in 64 bit Long Mode (so tables are required). Them you switch to 64b Linux, ASAP. Well, you are trying to boot within 300 to 500 msec, I see. It is a tough requirement, since these critical embedded applications MUST have rebooting times virtually set to 0. Imagine unmanned plane hit by fire, but still flying, or missile (cruse one, or you name it) hit by fire... Not a pretty picture for the inside system control! ;-)
Zoran
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Zoran Stojsavljevic