linux-kernel - Re: [REGRESSION][v4.9.y][v4.10.y] x86/efi: Only map RAM into EFI page tables if in mixed-mode

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Date:   Thu, 2 Feb 2017 20:34:31 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Joseph Salisbury <joseph.salisbury@...onical.com>
Cc:     Matt Fleming <matt@...eblueprint.co.uk>, waiman.long@....com,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Theodore Ts'o" <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
        Greg KH <gregkh@...uxfoundation.org>, scott.norton@....com,
        doug.hatch@....com,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [REGRESSION][v4.9.y][v4.10.y] x86/efi: Only map RAM into EFI page
 tables if in mixed-mode

On 2 February 2017 at 20:17, Joseph Salisbury
<joseph.salisbury@...onical.com> wrote:
> Hi Matt,
>
> A kernel bug report was opened against Ubuntu [0].  After a kernel
> bisect, it was found that reverting the following commit resolved this bug:
>
> commit 1297667083d5442aafe3e337b9413bf02b114edb
> Author: Matt Fleming <matt@...eblueprint.co.uk>
> Date:   Mon Sep 19 13:09:09 2016 +0100
>
>     x86/efi: Only map RAM into EFI page tables if in mixed-mode
>
>
> The regression was introduced as of v4.8-rc8.  It also still affects
> current mainline.
>
> I was hoping to get your feedback, since you are the patch author.  Do
> you think gathering any additional data will help diagnose this issue,
> or would it be best to submit a revert request?
>

Does this patch help at all?

https://git.kernel.org/cgit/linux/kernel/git/efi/efi.git/commit/?h=urgent&id=090abfc9dc7faf3f84799f956158c8c3af149a81