Re: [Bug #16173] After uncompressing the kernel, at boot time, the server hangs.

Eric W. Biederman
2010-08-29T23:49:06Z

"Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org> writes:

> On Monday, August 30, 2010, Eric W. Biederman wrote:
>> "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org> writes:
>>
>> > This message has been generated automatically as a part of a report
>> > of regressions introduced between 2.6.34 and 2.6.35.
>> >
>> > The following bug entry is on the current list of known regressions
>> > introduced between 2.6.34 and 2.6.35. Please verify if it still should
>> > be listed and let the tracking team know (either way).
>> >
>>
>> Looks like it's fixed.
>
> Good. What mainlne commit is that?

commit 910081322bf9c4ed392dc8f2ecbc33fdb42a2958
Author: Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Date: Wed Aug 4 12:51:11 2010 -0700

x86/apic: Map the local apic when parsing the MP table.

This fixes a regression in 2.6.35 from 2.6.34, that is
present for select models of Intel cpus when people are
using an MP table.

The commit cf7500c0ea133d66f8449d86392d83f840102632
"x86, ioapic: In mpparse use mp_register_ioapic" started
calling mp_register_ioapic from MP_ioapic_info. An extremely
simple change that was obviously correct. Unfortunately
mp_register_ioapic did just a little more than the previous
hand crafted code and so we gained this call path.

The problem call path is:
MP_ioapic_info()
mp_register_ioapic()
io_apic_unique_id()
io_apic_get_unique_id()
get_physical_broadcast()
modern_apic()
lapic_get_version()
apic_read(APIC_LVR)

Which turned out to be a problem because the local apic
was not mapped, at that point, unlike the similar point
in the ACPI parsing code.

This problem is fixed by mapping the local apic when
parsing the mptable as soon as we reasonably can.

Looking at the number of places we setup the fixmap for
the local apic, I see some serious simplification opportunities.
For the moment except for not duplicating the setting up of the
fixmap in init_apic_mappings, I have not acted on them.

The regression from 2.6.34 is tracked in bug
https://bugzilla.kernel.org/show_bug.cgi?id=16173

Cc: stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Reported-by: David Hill <hilld-HTiBYHdybX7UkGsOFmftXw@public.gmane.org>
Reported-by: Tvrtko Ursulin <tvrtko.ursulin-j34lQMj1tz/QT0dZR+AlfA@public.gmane.org>
Tested-by: Tvrtko Ursulin <tvrtko.ursulin-j34lQMj1tz/QT0dZR+AlfA@public.gmane.org>
Signed-off-by: Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>