Re: [GIT PULL] x86/urgent for v5.13-rc5

[Sasha Levin]

On Mon, Jun 07, 2021 at 12:07:58AM +0200, Borislav Petkov wrote:
> On Sun, Jun 06, 2021 at 02:23:21PM -0700, Linus Torvalds wrote:
> > On Sun, Jun 6, 2021 at 1:58 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
> > >
> > > A while ago hpa said:
> > >
> > >         As far as I know, Windows 7 actually reserves all memory below
> > >         1 MiB to avoid BIOS bugs.
> > >
> > > (https://bugzilla.kernel.org/show_bug.cgi?id=16661#c2)
> >
> > It would be good to have that checked somehow.
> >
> > I don't think this matters on any machine with gigs of RAM, but I do
> > wonder about the people who want to do small configurations. Maybe
> > they've given up on x86?
> >
> > It also eats into that somewhat precious legacy DMA resource and eats
> > up a fair chunk of that. Again, not an issue on modern hardware, but
> > ..
> >
> > > I believe that reserving everything below 1M after the real mode trampoline
> > > is allocated reduces amount of hidden dependencies and makes things simpler
> > > overall.
> >
> > Simpler, perhaps, and _I_ personally don't care about about 512kB of
> > memory any more on any machines I have, but ..
>
> Let's see if Sasha can dig out something... CCed.
>
> @Sasha, can you figure out who we can talk to whether Windoze reserves
> the first megabyte of memory unconditionally?

That's a great question, but I can't help there anymore :)

Adding James Morris...

--
Thanks,
Sasha