linux-kernel - Re: [GIT PULL] x86/mm changes for v5.9

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Date:   Thu, 6 Aug 2020 12:02:40 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/mm changes for v5.9

On Thu, Aug 6, 2020 at 11:57 AM Joerg Roedel <jroedel@...e.de> wrote:
>
> On Thu, Aug 06, 2020 at 03:10:34PM +0200, Ingo Molnar wrote:
> >
> > * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > > So apparently the "the page-table pages are all pre-allocated now" is
> > > simply not true. Joerg?
>
> It pre-allocates the whole vmalloc/ioremap PUD/P4D pages, but I actually
> only tested it with 4-level paging, as I don't have access to 5-level
> paging hardware.

I don't think Jason has either.

The

        PGD 0 P4D 0

line tells us that "pgd_present()" is true, even though PGD is 0
(otherwise it wouldn't print the P4D part). That means that he doesn't
have l5 enabled.

But you may obviously have different settings for CONFIG_X86_5LEVEL,
and maybe that ends up changing something?

But since apparently it's not immediately obvious what the problem is,
I'll revert it for now.

                Linus