linux-kernel - Re: [PATCH] Fix resume on x86-32 machines

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Message-ID: <CALCETrUpDOSz3f33MC40fp_o9Z0vRzchz9g5MUCgFOp6L9-U4Q@mail.gmail.com>
Date:   Mon, 11 Dec 2017 08:26:58 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Pavel Machek <pavel@....cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH] Fix resume on x86-32 machines

On Mon, Dec 11, 2017 at 7:13 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Andy Lutomirski <luto@...capital.net> wrote:
>
>>
>>
>> > On Dec 10, 2017, at 1:38 PM, Pavel Machek <pavel@....cz> wrote:
>> >
>> >
>> > After 4.15-rc2, suspend stopped working on Thinkpad X60. 5b06bbc
>> > (unintentionally?) reordered stuff with respect to
>> > fix_processor_context() on 32-bit and 64-bit. We undo that change on
>> > 32-bit.
>> >
>>
>> Can you explain what was wrong with the reordering?  Your patch certainly *looks* incorrect.
>>
>> I'm guessing that the real issue is that 32-bit needs %fs restored early for TLS.
>
> Does some early percpu primitive need GS as well perhaps?
>
> Might be safest to restore both FS and GS early.
>

fs needs to be restored early for TLS.  gs needs to be restored early,
maybe, if !X86_32_LAZY_GS -- it's used for stack-protector.  If
X86_32_LAZY_GS, gs must *not* be restored early.