linux-kernel - Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related?

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Date:	Thu, 19 Mar 2015 07:24:48 +0100
From:	Stefan Seyfried <stefan.seyfried@...glemail.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Jiri Kosina <jkosina@...e.cz>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Takashi Iwai <tiwai@...e.de>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>
Subject: Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related?

Good Morning :-)

Am 19.03.2015 um 01:57 schrieb Andy Lutomirski:

> Stefan, do you happen to know whether your disassembly of page_fault
> came from the instructions in memory or if they came from the vmlinux
> file?  Not that I have any relevant ideas there.

I think they came from memory. At least, the disassemble in crash...
crash> disassemble page_fault
Dump of assembler code for function page_fault:
   0xffffffff816834a0 <+0>:     data32 xchg %ax,%ax
   0xffffffff816834a3 <+3>:     data32 xchg %ax,%ax
   0xffffffff816834a6 <+6>:     data32 xchg %ax,%ax
   0xffffffff816834a9 <+9>:     sub    $0x78,%rsp
   0xffffffff816834ad <+13>:    callq  0xffffffff81683620 <error_entry>
   0xffffffff816834b2 <+18>:    mov    %rsp,%rdi
   0xffffffff816834b5 <+21>:    mov    0x78(%rsp),%rsi
   0xffffffff816834ba <+26>:    movq   $0xffffffffffffffff,0x78(%rsp)
   0xffffffff816834c3 <+35>:    callq  0xffffffff810504e0 <do_page_fault>
   0xffffffff816834c8 <+40>:    jmpq   0xffffffff816836d0 <error_exit>
End of assembler dump.

...is different than the one from loading vmlinux in gdb:

Reading symbols from vmlinux-4.0.0-rc3-2.gd5c547f-desktop...done.
Reading symbols from /usr/lib/debug/boot/vmlinux-4.0.0-rc3-2.gd5c547f-desktop.debug...done.
(gdb) disassemble page_fault
Dump of assembler code for function page_fault:
   0xffffffff816834a0 <+0>:     data16 xchg %ax,%ax
   0xffffffff816834a3 <+3>:     callq  *0x7a5b07(%rip)        # 0xffffffff81e28fb0 <pv_irq_ops+48>
   0xffffffff816834a9 <+9>:     sub    $0x78,%rsp
   0xffffffff816834ad <+13>:    callq  0xffffffff81683620 <error_entry>
   0xffffffff816834b2 <+18>:    mov    %rsp,%rdi
   0xffffffff816834b5 <+21>:    mov    0x78(%rsp),%rsi
   0xffffffff816834ba <+26>:    movq   $0xffffffffffffffff,0x78(%rsp)
   0xffffffff816834c3 <+35>:    callq  0xffffffff810504e0 <do_page_fault>
   0xffffffff816834c8 <+40>:    jmpq   0xffffffff816836d0 <error_exit>
End of assembler dump.

Best regards,

	Stefan
-- 
Stefan Seyfried
Linux Consultant & Developer -- GPG Key: 0x731B665B

B1 Systems GmbH
Osterfeldstraße 7 / 85088 Vohburg / http://www.b1-systems.de
GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt,HRB 3537
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