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From: Andy Lutomirski <luto@kernel.org>
Date: Mon, 11 Dec 2017 08:26:58 -0800
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Subject: Re: [PATCH] Fix resume on x86-32 machines
To: Ingo Molnar <mingo@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Zhang Rui <rui.zhang@intel.com>, Andrew Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jarkko Nikula <jarkko.nikula@linux.intel.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Mon, Dec 11, 2017 at 7:13 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Andy Lutomirski <luto@amacapital.net> wrote:
>
>>
>>
>> > On Dec 10, 2017, at 1:38 PM, Pavel Machek <pavel@ucw.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.