Re: [PATCH] x86/boot: Reorganize and clean up the BIOS area reservation code
From: Linus Torvalds
Date: Fri Jul 22 2016 - 21:17:05 EST
On Fri, Jul 22, 2016 at 10:00 PM, Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote:
> I suppose we could rewrite the page table mapping for those precious
> <1MB regions to coerce the firmware into accessing different pages
> instead of the 1:1 addresses and copy the regions elsewhere. Maybe.
> That assumes we don't hit other firmware bugs though.
.. it also assumes that firmware honors our page tables. Which at a
minimum won't be true for things like SMM, which happens with paging
And that's exactly the kind of code that touches some of the memory in
the low 1M region - things like the legacy keyboard state bits in the
low 4kB etc, for crazy old DOS days, iirc.