linux-kernel - Re: [tip:x86/pti] x86/cpu_entry_area: Sync cpu_entry_area to initial_page

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Date:   Thu, 1 Mar 2018 10:31:11 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     tglx@...utronix.de, hpa@...or.com, linux-kernel@...r.kernel.org,
        william.grant@...onical.com, terraluna977@...il.com
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/pti] x86/cpu_entry_area: Sync cpu_entry_area to
 initial_page_table


Just a few small speling nits:

* tip-bot for Thomas Gleixner <tipbot@...or.com> wrote:

> Commit-ID:  945fd17ab6bab8a4d05da6c3170519fbcfe62ddb
> Gitweb:     https://git.kernel.org/tip/945fd17ab6bab8a4d05da6c3170519fbcfe62ddb
> Author:     Thomas Gleixner <tglx@...utronix.de>
> AuthorDate: Wed, 28 Feb 2018 21:14:26 +0100
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Thu, 1 Mar 2018 09:48:27 +0100
> 
> x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table
> 
> The separation of the cpu_entry_area from the fixmap missed the fact that
> on 32bit non-PAE kernels the cpu_entry_area mapping might not be covered in
> initial_page_table by the previous synchronizations.
> 
> This results in suspend/resume failures because 32bit utilizes initial page
> table for resume. The absence of the cpu_entry_area mapping results in a
> triple fault, aka. insta reboot.
> 
> With PAE enabled this works by chance because the PGD entry which covers
> the fixmap and other parts incindentally provides the cpu_entry_area
> mapping as well.

s/incindentally/incidentally

s/32bit/32-bit

s/utilizes initial page table
 /utilizes the initial page table

> Synchronize the initial page table after setting up the cpu entry
> area. Instead of adding yet another copy of the same code, move it to a
> function and invoke it from the various places.

s/cpu/CPU

> It needs to be investigated if the existing calls in setup_arch() and
> setup_per_cpu_areas() can be replaced by the later invocation from
> setup_cpu_entry_areas(), but that's beyond the scope of this fix.

> +	/*
> +	 * This is the last essential update to swapper_pgdir which needs
> +	 * to be synchronized to initial_page_table on 32bit.
> +	 */
> +	sync_initial_page_table();


s/swapper_pgdir
 /swapper_pg_dir

s/on 32bit/on 32-bit kernels

> +	/*
> +	 * sync back low identity map too.  It is used for example
> +	 * in the 32-bit EFI stub.
> +	 */

s/sync/Sync

Very nice fix!

Thanks,

	Ingo