linux-kernel - Re: [Bisected][-next-20130204+] [x86/kvm] udevd:[97]: segfault at ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d

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Date:	Wed, 13 Feb 2013 06:57:09 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [Bisected][-next-20130204+] [x86/kvm] udevd:[97]: segfault at
 ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d

On Wed, 2013-02-13 at 12:51 +0200, Gleb Natapov wrote:
> On Tue, Feb 12, 2013 at 04:39:03PM -0800, H. Peter Anvin wrote:
> > On 02/12/2013 04:26 PM, Peter Hurley wrote:
> > > With -next-20130204+ in ubuntu 12.10 VM (so the 80x25 VGA
> > > device/console):
> > > 
> > > [    0.666410] udevd[97]: starting version 175
> > > [    0.674043] udevd[97]: udevd:[97]: segfault at ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d
> > > 
> > > and boots to an initramfs prompt.
> > > 
> > > git bisect (log attached) blames:
> > > 
> > > commit 7b5c4a65cc27f017c170b025f8d6d75dabb11c6f
> > > Merge: 3596f5b 949db15
> > > Author: H. Peter Anvin <hpa@...ux.intel.com>
> > > Date:   Fri Jan 25 16:31:21 2013 -0800
> > > 
> > >     Merge tag 'v3.8-rc5' into x86/mm
> > >     
> > >     The __pa() fixup series that follows touches KVM code that is not
> > >     present in the existing branch based on v3.7-rc5, so merge in the
> > >     current upstream from Linus.
> > >     
> > >     Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> > > 
> > > 
> > > This only happens with the VGA device/console but that is the default
> > > configuration for Ubuntu/KVM because it blacklists pretty much every fb
> > > driver.
> > > 
> > 
> > I am guessing this is another bad use of __pa()... need to look into that.
> > 
> He is using 64bit guest and on those __pa() happens to be working. Is it
> possible that slow_virt_to_phys() does not work as expected? Peter (the
> bug reporter :)) can you run your guest kernel with loglevel=7 and
> attach send me console output?

Attached.

BTW, this message happens on 'good' boots too:

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: at /home/peter/src/kernels/next/arch/x86/kernel/pvclock.c:182 pvclock_init_vsyscall+0x22/0x60()
[    0.000000] Hardware name: Bochs
[    0.000000] Modules linked in:
[    0.000000] Pid: 0, comm: swapper Not tainted 3.8.0-next-20130204-xeon #20130204
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff8105812f>] warn_slowpath_common+0x7f/0xc0
[    0.000000]  [<ffffffff8105818a>] warn_slowpath_null+0x1a/0x20
[    0.000000]  [<ffffffff81d20521>] pvclock_init_vsyscall+0x22/0x60
[    0.000000]  [<ffffffff81d20480>] kvm_setup_vsyscall_timeinfo+0x74/0xd8
[    0.000000]  [<ffffffff81d201d1>] kvm_guest_init+0xd0/0xe9
[    0.000000]  [<ffffffff81d13f7c>] setup_arch+0xbee/0xcaf
[    0.000000]  [<ffffffff816cbceb>] ? printk+0x61/0x63
[    0.000000]  [<ffffffff81d0cbc3>] start_kernel+0xd3/0x3f0
[    0.000000]  [<ffffffff81d0c5e4>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81d0c6d7>] x86_64_start_kernel+0xf1/0x100
[    0.000000] ---[ end trace b47bb564b2d6ec76 ]---

Regards,
Peter Hurley

View attachment "segfault_dmesg.log" of type "text/x-log" (25112 bytes)