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Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up

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On Mon, May 8, 2017 at 9:31 AM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 2017-03-23 10:14, tip-bot for Andy Lutomirski wrote:
>> The x86 smpboot trampoline expects initial_page_table to have the
>> GDT mapped.  If the GDT ends up in a virtually mapped per-cpu page,
>> then it won't be in the page tables at all until perc-pu areas are
>> set up.  The result will be a triple fault the first time that the
>> CPU attempts to access the GDT after LGDT loads the perc-pu GDT.
>>
>> This appears to be an old bug, but somehow the GDT fixmap rework
>> is triggering it.  This seems to have something to do with the
>> memory layout.

> This breaks the boot on our Intel Quark platform (IOT2000, similar to
> Galileo Gen2). Reverting it over master makes it work again. Any idea
> what goes wrong? Let me know how I can help debugging this.

JFYI: As of today linux-next when _kexec:ed_ works fine to me

Perhaps I can test this later with direct boot from SD card.

-- 
With Best Regards,
Andy Shevchenko

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Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Jan Kiszka <jan.kiszka@siemens.com> - 2017-05-08 08:40 +0200
  Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-05-08 11:40 +0200
    Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Andy Lutomirski <luto@kernel.org> - 2017-05-08 13:30 +0200
      Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Jan Kiszka <jan.kiszka@siemens.com> - 2017-05-08 14:40 +0200
        Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-05-08 16:50 +0200
          Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Jan Kiszka <jan.kiszka@siemens.com> - 2017-05-08 17:30 +0200
        Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Jan Kiszka <jan.kiszka@siemens.com> - 2017-05-08 20:00 +0200
          Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table  until per-cpu is set up Andy Lutomirski <luto@kernel.org> - 2017-05-09 02:10 +0200

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