right, Aaron, you keep reminding me of that and I keep forgetting it :-)
so, ok, ramstage it is for paging. The x86 is so darned annoying. We had paging in the bootblock for PPC on linuxbios.
On Wed, Aug 2, 2017 at 12:43 PM Aaron Durbin adurbin@google.com wrote:
On Wed, Aug 2, 2017 at 1:36 PM, ron minnich rminnich@gmail.com wrote:
On Wed, Aug 2, 2017 at 12:08 PM Zoran Stojsavljevic zoran.stojsavljevic@gmail.com wrote:
So, turning on the Virtual Mode (paging ON), you'll also imply that Coreboot will initialize and use MMU, don't you?
sure.
Am I correct, or you can use paging without MMU?!
MMU must be on.
I doubt that, perhaps. So, then, I would like to see this code in
Coreboot
where MMU is initialized. And how it is initialized (maybe there is a
some
over-simplified mode of operation using 2MB pages).
yep.
And my question is: what for? Or I did not get the idea... Who really needs to use paging in boot-loaders? Even INTEL, which (on purpose)
makes
things way over-dimensioned and over-complicated, does NOT use paging in UEFI BIOSes, so far???
it's trivial to turn on paging. In harvey I've got it down to 160 lines, including comments and white space. I made it much more compact in my CL from 1/2014.
If you turn on paging you can capture null pointer derefs, and all other
out
of range address references. And relocatable modules are much easier..
My question is, why not do it? I don't see any harm. All the other
platforms
in coreboot use paging. What's so special about x86 that it should not
use
paging?
You can't use it for CAR so that sorta throws out romstage and before. It's up to the implementation of how CAR works within the hierarchy, but with hardware page walkers that pull things through the cache things can go badly. So then you could enable paging for ramstage. Need to locate storage for the page tables, but that's not an impossible thing either.
ron
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ron minnich