From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Clayton <chris2553@googlemail.com>
Subject: Re: qemu-kvm-1.1.0 crashing with kernel 3.5.0-rc6
Date: Sun, 29 Jul 2012 18:50:09 +0100
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Cc: Eric Northup <digitaleric@google.com>, kvm@vger.kernel.org,
	Gleb Natapov <gleb@redhat.com>,
	Jan Kiszka <jan.kiszka@siemens.com>
To: Avi Kivity <avi@redhat.com>
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On 07/29/12 17:34, Avi Kivity wrote:
> On 07/29/2012 06:47 PM, Avi Kivity wrote:
>>> What might have happened is that the movdqu instruction faulted (as it's
>>> an fpu instruction), and on the way back from the fault, ds and es
>>> didn't get restored correctly.
>>>
>>> You can test this by writing a trivial version of g_str_equal()
>>> somewhere in the qemu source code and rebuilding it.
>>>
>>>
>>
>> from entry_32.S:
>>
>> .macro RESTORE_REGS pop=0
>> 	RESTORE_INT_REGS
>> 1:	popl_cfi %ds
>> 	/*CFI_RESTORE ds;*/
>> 2:	popl_cfi %es
>> 	/*CFI_RESTORE es;*/
>> 3:	popl_cfi %fs
>> 	/*CFI_RESTORE fs;*/
>> 	POP_GS \pop
>> .pushsection .fixup, "ax"
>> 4:	movl $0, (%esp)
>> 	jmp 1b
>> 5:	movl $0, (%esp)
>> 	jmp 2b
>> 6:	movl $0, (%esp)
>> 	jmp 3b
>> .popsection
>>
>> this piece of code tries to restore %ds, and if it fails, zeros it,
>> which is consistent with the core dump.
>>
>> This could happen if kvm is failing to restore GDT correctly.
>>
>
> Possible culprit: b2da15ac26a0c00.
>
>
That commit isn't in qermu-kvm-1.1.1.

I'm testing a build with g_str_equal implemented in kvm.c and so far I 
haven't had a crash in 6 invocations. That hasn't been possible with 
vanilla qemu-kvm-1.1.{0,1}, but I'll do a few more, just to be sure.

Thanks for your help, Avi.