Re: [PATCH v2 0/6] Add initial support for booting x86_64 from grub

[Samuel Thibault]

Luca, le dim. 28 août 2022 09:54:43 +0200, a ecrit:
> Il 27 agosto 2022 20:02:40 UTC, Samuel Thibault <samuel.thibault@gnu.org> ha
> scritto:
> > Samuel Thibault, le sam. 27 août 2022 21:41:57 +0200, a ecrit:
> > > Mmm, on the set_cr3() in i386at_init call, it reboots...
> > 
> > Ah, reducing the memory size to 2G fixed it. The kernel_pmap->l4base
> > address was at 0xFFFD3000, apparently that was going up the roof :)
> > It'd be useful to test with larger memory sizes, since that's one of the
> > points of going 64bit ;)
> 
> Yes that is still a limitation, I forgot to add it to the commit
> description. I think the simplest way to solve it would be to link to the
> upper 2G and enhance pmap to handle L4 tables, but I was trying to have
> something running until a shell prompt first :)

Sure, but then please put something that caps the memory, so that
people don't trap into the pitfall (they don't usually read the source
code...)

> On 64 bit we could also remove the direct mapping of all the phisical pages,
> right? IIRC it's needed only by the linux drivers.

We'll probably be able to remove that, yes.

Samuel