From: Borislav Petkov <bp@amd64.org>
To: Tejun Heo <tj@kernel.org>
Cc: "Herrmann3, Andreas" <Andreas.Herrmann3@amd.com>,
"Seidel, Conny" <Conny.Seidel@amd.com>,
Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: WARNING: at arch/x86/kernel/apic/apic.c:1239 setup_local_APIC+...
Date: Fri, 14 Oct 2011 18:56:04 +0200 [thread overview]
Message-ID: <20111014165604.GA14286@aftab> (raw)
In-Reply-To: <20111014135516.GC11990@aftab>
On Fri, Oct 14, 2011 at 09:55:16AM -0400, Borislav Petkov wrote:
> So, in the end, and AFAICR, the warning triggers because we're comparing
> logical APIC IDs from the APIC Logical Destination Register (0xD0) which
> have been assigned by BIOS with "1 << cpu" shifted values which wrap on
> 32-bit.
>
> I'd very much like to know why?
Update: upon a second thought, we think we know why: The WARN_ON
cannot stomach the switch to bigsmp apic because, on the one hand,
bigsmp_init_apic_ldr() "normalizes" the APIC ids by using the BIOS
values (x86_bios_cpu_apicid) but OTOH, x86_cpu_to_logical_apicid
contains the early percpu value which got assigned by the default apic,
i.e. the shifting thing as it is spec'ed for the LDR register.
So, the way we see it, the WARN_ON should know whether we switched apics
or should be removed completely. Btw, why was it added in the first
place, the commit message doesn't quite explain why.
Thanks.
--
Regards/Gruss,
Boris.
Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551
next prev parent reply other threads:[~2011-10-14 16:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-14 13:55 WARNING: at arch/x86/kernel/apic/apic.c:1239 setup_local_APIC+ Borislav Petkov
2011-10-14 16:56 ` Borislav Petkov [this message]
2011-10-14 17:55 ` Tejun Heo
2011-10-15 22:12 ` Borislav Petkov
2011-10-16 22:07 ` Conny Seidel
2011-10-17 7:23 ` Borislav Petkov
2011-10-17 7:38 ` Ingo Molnar
2011-10-17 7:53 ` Borislav Petkov
2011-10-17 7:23 ` Jan Beulich
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20111014165604.GA14286@aftab \
--to=bp@amd64.org \
--cc=Andreas.Herrmann3@amd.com \
--cc=Conny.Seidel@amd.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox