linux-kernel - [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 15:17:29 -0500
From:   Joseph Salisbury <joseph.salisbury@...onical.com>
To:     matt@...eblueprint.co.uk
Cc:     waiman.long@....com, ard.biesheuvel@...aro.org,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>, 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,
        linux-efi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [REGRESSION][v4.9.y][v4.10.y] x86/efi: Only map RAM into EFI page
 tables if in mixed-mode

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?


Thanks,

Joe

[0] http://pad.lv/1659340