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 <[email protected]> wrote: > On Wed, Aug 2, 2017 at 1:36 PM, ron minnich <[email protected]> wrote: > > > > > > On Wed, Aug 2, 2017 at 12:08 PM Zoran Stojsavljevic > > <[email protected]> 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 > > > > -- > > coreboot mailing list: [email protected] > > https://mail.coreboot.org/mailman/listinfo/coreboot >
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