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

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Message-Id: <51e60223-0d5d-428e-9126-2754020f19a1@app.fastmail.com>
Date:   Thu, 02 Mar 2023 08:14:06 -0800
From:   "Andy Lutomirski" <luto@...nel.org>
To:     "Michael Kelley" <mikelley@...rosoft.com>,
        "James Morris" <jmorris@...ei.org>,
        "Sasha Levin" <sashal@...nel.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Mike Rapoport" <rppt@...ux.ibm.com>,
        "Borislav Petkov" <bp@...en8.de>
Cc:     "the arch/x86 maintainers" <x86@...nel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "James Morris" <James.Morris@...rosoft.com>
Subject: Re: [GIT PULL] x86/urgent for v5.13-rc5

On Tue, Jun 8, 2021, at 10:53 AM, Michael Kelley wrote:
> From: James Morris <jmorris@...ei.org> Sent: Monday, June 7, 2021 11:47 AM
>> 
>> On Sun, 6 Jun 2021, Sasha Levin wrote:
>> 
>> > >
>> > >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...
>> 
>> Adding Michael Kelley.
>> 
>
> I checked with the Windows team.  Peter Anvin's statement from 11
> years ago is true.  On Intel and AMD processors, Windows unconditionally
> reserves the 1st megabyte of memory, minus one page used for real
> mode startup.   This is done to work around BIOS bugs.

Sorry to dredge up old skeletons.  Do you know *where* Windows allocates that one page used for real mode startup?  The current code in Linux has some bugs allocating that page, and it would be nice to sort it out.