From: Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Andy Shevchenko
<andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Jan Kiszka <jan.kiszka-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
x86 <x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-efi <linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"Peter Zijlstra (Intel)"
<peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Boris Ostrovsky
<boris.ostrovsky-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Matt Fleming
<matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Juergen Gross <jgross-IBi9RG/b67k@public.gmane.org>,
Ard Biesheuvel
<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up
Date: Mon, 8 May 2017 04:21:29 -0700 [thread overview]
Message-ID: <CALCETrXzzhoyzyqp5s7sSOkAtsR2Cor6j+x16OLv=+G30Y6+WQ@mail.gmail.com> (raw)
In-Reply-To: <CAHp75VdX-kUqW0MKOSTz9zByU-eipBMnKpdUbTt2SVOJ8Kvrig-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Mon, May 8, 2017 at 2:32 AM, Andy Shevchenko
<andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Mon, May 8, 2017 at 9:31 AM, Jan Kiszka <jan.kiszka-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org> 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.
>
The most likely explanation is that there's some code that needs the
page table synced and runs before setup_per_cpu_areas(). The relevant
init code is:
setup_arch(&command_line);
mm_init_cpumask(&init_mm);
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();
so I didn't move it very far. It would be awesome if we could get a
backtrace when the failure happens, but it's likely to be a triple
fault. Is this an EFI boot? I bet the failure is in efi_init().
Could you try reverting just the deletions in the patch? I.e. try a
kernel with both the old and the new copies of the code I moved.
--Andy
next prev parent reply other threads:[~2017-05-08 11:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1490218061.git.luto@kernel.org>
[not found] ` <cover.1490218061.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2017-03-22 21:32 ` [PATCH 3/7] x86/efi/32: Fix EFI on systems where the percpu GDT is virtually mapped Andy Lutomirski
2017-03-22 21:32 ` [PATCH 4/7] x86/boot/32: Defer resyncing initial_page_table until percpu is set up Andy Lutomirski
[not found] ` <tip-23b2a4ddebdd17fad265b4bb77256c2e4ec37dee@git.kernel.org>
[not found] ` <tip-23b2a4ddebdd17fad265b4bb77256c2e4ec37dee-Ckxz5ZWcFp/9qxiX1TGQuw@public.gmane.org>
2017-05-08 6:31 ` [tip:x86/mm] x86/boot/32: Defer resyncing initial_page_table until per-cpu " Jan Kiszka
[not found] ` <0c4d6d04-7038-fb82-87b3-343784550d0a-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>
2017-05-08 9:32 ` Andy Shevchenko
[not found] ` <CAHp75VdX-kUqW0MKOSTz9zByU-eipBMnKpdUbTt2SVOJ8Kvrig-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-08 11:21 ` Andy Lutomirski [this message]
2017-05-08 12:34 ` Jan Kiszka
[not found] ` <7f5916b5-01c0-52d5-9f44-dee4bf355212-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>
2017-05-08 14:45 ` Andy Shevchenko
2017-05-08 15:24 ` Jan Kiszka
2017-05-08 17:53 ` Jan Kiszka
[not found] ` <7ce941e5-5a9b-acd7-c7b6-7be464572de5-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>
2017-05-09 0:03 ` Andy Lutomirski
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