linux-kernel - Re: 2.6.22-rc1-mm1: strange GPF when panicing under kvm

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Message-ID: <464C574C.5020201@qumranet.com>
Date:	Thu, 17 May 2007 16:23:24 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.22-rc1-mm1: strange GPF when panicing under kvm

Jeremy Fitzhardinge wrote:
> When I boot 2.6.22-rc1-mm1 under kvm, but forget to specify a root
> filesystem, it panics as expected.  However, when panicing, it gets a
> GPF in delay_tsc, and then starts recursively panicing.
>
> I don't really understand what's going on; the instruction it's faulting
> on seems to be "pause" (ie, rep;nop), which seems like it shouldn't
> fault at all.  It looks like some kvm artifact to me, but I'm not sure.
>
> Hm, given the error code, maybe it's a segment register problem.
>
>   

Strange.  What does your msr 0x482 look like?  If you have 
/dev/cpu/0/msr, the following will spit it out:

-------------
#!/usr/bin/python

import struct

msrs = file('/dev/cpu/0/msr')
msrs.seek(0x482)
msr = msrs.read(8)
msr = struct.unpack('Q', msr)[0]

print '%x' % (msr,)
----------------

(that msr can force trapping of the pause instruction, even though 
there's no good reason to do it, and kvm wouldn't inject a gp if it did 
anyway).

-- 
error compiling committee.c: too many arguments to function

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