linux-kernel - Re: kvm: unable to handle kernel NULL pointer dereference

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Message-ID: <20080605072728.GF30402@sequoia.sous-sol.org>
Date:	Thu, 5 Jun 2008 00:27:28 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Tobias Diedrich <ranma+kernel@...edrich.de>,
	Chris Wright <chrisw@...s-sol.org>,
	Avi Kivity <avi@...ranet.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: kvm: unable to handle kernel NULL pointer dereference

* Tobias Diedrich (ranma+kernel@...edrich.de) wrote:
> Almost:
> ranma@...chior:~/src/linux-2.6.26-rc4.forcedwol$ gdb -q vmlinux
> Using host libthread_db library "/lib/libthread_db.so.1".
> (gdb)  p/x 0xffffffff8021d456 + 0x6f9cba
> $1 = 0xffffffff80917110
> (gdb) p/x &per_cpu__svm_data
> $2 = 0xffffffff809170f8
> (gdb) 

Sorry, my math was bad.  I gave you 0xffffffff8021d44f + 7 + 0x6f9cba,
but it should have been 0xffffffff8021d44f - 17 + 0x6f9cba.  Which is
correct (as one would hope, it was a grasp at straws).

Oh, wait.  Is this a laptop?  Do you suspend/resume?  Suspend will free
svm_data, and on resume, any launching a guest will definitely hit the
oops you are seeing.

Do you ever see this in dmesg?

  svm_cpu_init: svm_data is NULL on 0

thanks,
chris
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