linux-kernel - Re: [bisected] 2.6.31 regression: fails to boot as xen guest

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Date:	Tue, 25 Aug 2009 18:49:30 +0200
From:	Arnd Hannemann <hannemann@...s.rwth-aachen.de>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	Arnd Hannemann <Arnd.Hannemann@...s.rwth-aachen.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [bisected] 2.6.31 regression: fails to boot as xen guest

Hi Pekka,

Pekka Enberg wrote:
> On Tue, Aug 25, 2009 at 6:48 PM, Arnd
> Hannemann<hannemann@...s.rwth-aachen.de> wrote:
>> current 2.6.31 fails to boot on our xen host (32bit pae).
>> Unfortunately it fails in a way that there is absolutely no output
>> on the console. Config is as 32bit guest.
>>
>> Git bisect gave the following:
>>
>> 83b519e8b9572c319c8e0c615ee5dd7272856090 is first bad commit commit
>> 83b519e8b9572c319c8e0c615ee5dd7272856090 Author: Pekka Enberg
>> <penberg@...helsinki.fi> Date:   Wed Jun 10 19:40:04 2009 +0300
>>
>> slab: setup allocators earlier in the boot sequence
>>
>> This patch makes kmalloc() available earlier in the boot sequence
>> so we can get rid of some bootmem allocations. The bulk of the
>> changes are due to kmem_cache_init() being called with interrupts
>> disabled which requires some changes to allocator boostrap code.
>>
>> Note: 32-bit x86 does WP protect test in mem_init() so we must
>> setup traps before we call mem_init() during boot as reported by
>> Ingo Molnar:
>>
>> We have a hard crash in the WP-protect code:
>>
>> [    0.000000] Checking if this processor honours the WP bit even
>> in supervisor mode...BUG: Int 14: CR2 ffcff000 [    0.000000]
>> EDI 00000188  ESI 00000ac7  EBP c17eaf9c  ESP c17eaf8c [
>> 0.000000]      EBX 000014e0  EDX 0000000e  ECX 01856067  EAX
>> 00000001 [    0.000000]      err 00000003  EIP c10135b1   CS
>> 00000060  flg 00010002 [    0.000000] Stack: c17eafa8 c17fd410
>> c16747bc c17eafc4 c17fd7e5 000011fd f8616000 c18237cc [
>> 0.000000]        00099800 c17bb000 c17eafec c17f1668 000001c5
>> c17f1322 c166e039 c1822bf0 [    0.000000]        c166e033 c153a014
>> c18237cc 00020800 c17eaff8 c17f106a 00020800 01ba5003 [
>> 0.000000] Pid: 0, comm: swapper Not tainted
>> 2.6.30-tip-02161-g7a74539-dirty #52203 [    0.000000] Call Trace: [
>> 0.000000]  [<c15357c2>] ? printk+0x14/0x16 [    0.000000]
>> [<c10135b1>] ? do_test_wp_bit+0x19/0x23 [    0.000000]
>> [<c17fd410>] ? test_wp_bit+0x26/0x64 [    0.000000]  [<c17fd7e5>] ?
>> mem_init+0x1ba/0x1d8 [    0.000000]  [<c17f1668>] ?
>> start_kernel+0x164/0x2f7 [    0.000000]  [<c17f1322>] ?
>> unknown_bootoption+0x0/0x19c [    0.000000]  [<c17f106a>] ?
>> __init_begin+0x6a/0x6f
>>
>> Acked-by: Johannes Weiner <hannes@...xchg.org> Acked-by Linus
>> Torvalds <torvalds@...ux-foundation.org> Cc: Christoph Lameter
>> <cl@...ux-foundation.org> Cc: Ingo Molnar <mingo@...e.hu> Cc: Matt
>> Mackall <mpm@...enic.com> Cc: Nick Piggin <npiggin@...e.de> Cc:
>> Yinghai Lu <yinghai@...nel.org> Signed-off-by: Pekka Enberg
>> <penberg@...helsinki.fi>
>>
>> However a git revert 83b519e8b9572c319c8e0c615ee5dd7272856090 to
>> verify that current git without that commit would work, didn't
>> succeed right away, so I was not able to test that.
>
> Thanks for doing the bisect! Can we also see your .config also?

Config for -rc7 is attached. My bisect configs were based on that.

>
> I doubt this is a slab allocator initialization issue so I'm CC'ing
> some Xen folks. Jeremy, I don't know Xen well but on quick read, the
> only thing that I can see is that trap_init() is called before
> sched_init() now. I see Xen doing preempt_enable()/preempt_disable so
>  maybe that's a problem now?
>
> Pekka

Best regards,
Arnd


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