linux-kernel - Re: 2.6.25-rc1 xen pvops regression

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Date:	Sat, 16 Feb 2008 13:44:26 +1100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Jody Belka <lists-lkml@...b.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ian Campbell <ijc@...lion.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andi Kleen <andi@...stfloor.org>,
	Mika Penttila <mika.penttila@...umbus.fi>
Subject: Re: 2.6.25-rc1 xen pvops regression

Joel Becker wrote:
> On Thu, Feb 14, 2008 at 06:50:52PM +1100, Jeremy Fitzhardinge wrote:
>   
>>> 	I'm seeing the same problem, with no messages at all from xen
>>> other than "domain crashed, restart disabled" in xend.log.  I got a
>>> different commit in my bisect, 0947b2f31ca1ea1211d3cde2dbd8fcec579ef395
>>> (i386 boot: replace boot_io    remap with enhanced bt_ioremap - enhance
>>> bt_ioremap).  I started from yesterday's
>>> 96b5a46e2a72dc1829370c87053e0cd558d58bc0 (WMI: initialize
>>> wmi_blocks.list even if ACPI is disabled) and a known good
>>> 9b73e76f3cf63379dcf45fcd4f112f5812418d0a (Merge
>>> git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6).
>>>       
>> Is the domain ending up in the crashed state?  Do you get a register  
>> dump with xm dmesg?  That would be very useful in determining what went  
>> wrong.  You may need to compile Xen with debug=y in Config.mk.
>>     
>
> 	I didn't know xm dmesg existed :-)  Regarding debug=y, I'm using
> a prepackaged dom0 set.  Here's what I find in xm dmesg:
>
> Joel
>
> (XEN) mm.c:1825:d109 Bad type (saw 0000000028000001 != exp 00000000e0000000) for mfn 3a2f0f (pfn f0)
> (XEN) mm.c:649:d109 Error getting mfn 3a2f0f (pfn f0) from L1 entry 00000003a2f0f063 for dom109
> (XEN) mm.c:1825:d109 Bad type (saw 0000000028000001 != exp 00000000e0000000) for mfn 3a2f0f (pfn f0)
> (XEN) mm.c:649:d109 Error getting mfn 3a2f0f (pfn f0) from L1 entry 00000003a2f0f063 for dom109
> (XEN) mm.c:3331:d109 ptwr_emulate: could not get_page_from_l1e()
>   

Hm, I have a suspicion about what this might be.  I'll haven't tried 
reproducing it yet though.

> (XEN) Unhandled page fault in domain 109 on VCPU 0 (ec=0003)
> (XEN) Pagetable walk from 00000000c01687f0:
> (XEN)  L4[0x000] = 00000003a2933027 00000000000006cc
> (XEN)  L3[0x003] = 000000039afea027 0000000000000005
> (XEN)  L2[0x000] = 000000039bfb7067 0000000000001048 
> (XEN)  L1[0x168] = 00000003a2e97061 0000000000000168
> (XEN) domain_crash_sync called from entry.S
> (XEN) Domain 109 (vcpu#0) crashed on cpu#2:
> (XEN) ----[ Xen-3.1.3-rc3  x86_64  debug=n  Not tainted ]----
> (XEN) CPU:    2
> (XEN) RIP:    e019:[<00000000c04040bd>]
>   

What does this EIP correspond to in your kernel?  Also:

c01687f0 c0417ab6 c040288f c040299a c0403270

(as guesses of potential callers to try and work out a stack trace).

Thanks,
	J


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