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Date:   Mon, 7 Jun 2021 00:07:58 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Cc:     Mike Rapoport <rppt@linux.ibm.com>, x86-ml <x86@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] x86/urgent for v5.13-rc5
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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@linux.ibm.com> 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?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette